Compositions and articles of manufacture

ABSTRACT

This invention relates generally to compositions and articles of manufacturing comprising single-wall carbon nanotubes (SWNTs). Tubular single-wall carbon nanotube molecules are useful for making electrical connectors for devices such as integrated circuits or semiconductor chips used in computers because of the high electrical conductivity and small size of the carbon molecule. SWNT molecules are also useful as components of electrical devices where quantum effects dominate at room temperatures, for example, resonant tunneling diodes. The metallic carbon molecules are useful as antennas at optical frequencies, and as probes for scanning probe microscopy such as are used in scanning tunneling microscopes (STM) and atomic force microscopes (AFM). Tubular carbon molecules may also be used in RF shielding applications, e.g., to make microwave absorbing materials.

BACKGROUND OF THE INVENTION

[0001] Fullerenes are closed-cage molecules composed entirely ofsp²-hybridized carbons, arranged in hexagons and pentagons. Fullerenes(e, C₆₀) were first identified as closed spheroidal cages produced bycondensation from vaporized carbon.

[0002] Fullerene tubes are produced in carbon deposits on the cathode incarbon arc methods of producing spheroidal fullerenes from vaporizedcarbon. Ebbesen et al. (Ebbesen I), “Large-Scale Synthesis Of CarbonNanotubes,” Nature, Vol. 358, p. 220 (Jul. 16, 1992) and Ebbesen et al.,(Ebbesen II), “Carbon Nanotubes,” Annual Review of Materials Science,Vol. 24, p. 235 (1994). Such tubes are referred to herein as carbonnanotubes. Many of the carbon nanotubes made by these processes weremulti-wall nanotubes, ie., the carbon nanotubes resembled concentriccylinders. Carbon nanotubes having up to seven walls have been describedin the prior art. Ebbesen II; Iijima et al., “Helical Microtubules OfGraphitic Carbon,” Nature, Vol. 354, p. 56 (Nov. 7, 1991).

[0003] Single-wall carbon nanotubes have been made in a DC arc dischargeapparatus of the type used in fullerene production by simultaneouslyevaporating carbon and a small percentage of Group VIII transition metalfrom the anode of the arc discharge apparatus. See Iijima et al.,“Single-Shell Carbon Nanotubes of 1 nm Diameter,” Nature, Vol. 363, p.603 (1993); Bethune et al., “Cobalt Catalyzed Growth of Carbon Nanotubeswith Single Atomic Layer Walls,” Nature, Vol. 63, p. 605 (1993); Ajayanet al., “Growth Morphologies During Cobalt Catalyzed Single-Shell CarbonNanotube Synthesis,” Chem. Phys. Lett., Vol. 215, p. 509 (1993); Zhou etal., “Single-Walled Carbon Nanotubes Growing Radially From YC₂Particles,” Appl. Phys. Lett., Vol. 65, p. 1593 (1994); Seraphin et al.,“Single-Walled Tubes and Encapsulation of Nanocrystals Into CarbonClusters,” Electrochem. Soc., Vol. 142, p. 290 (1995); Saito et al.,“Carbon Nanocapsules Encaging Metals and Carbides,” J. Phys. Chem.Solids, Vol. 54, p. 1849 (1993); Saito et al., “Extrusion of Single-WallCarbon Nanotubes Via Formation of Small Particles Condensed Near anEvaporation Source,” Chem. Phys. Lett., Vol 236, p. 419 (1995). It isalso known that the use of mixtures of such transition metals cansignificantly enhance the yield of single-wall carbon nanotubes in thearc discharge apparatus. See Lambert et al., “Improving ConditionsToward Isolating Single-Shell Carbon Nanotubes,” Chem. Phys. Lett., Vol.226, p. 364 (1994).

[0004] While this arc discharge process can produce single-wallnanotubes, the yield of nanotubes is low and the tubes exhibitsignificant variations in structure and size between individual tubes inthe mixture. Individual carbon nanotubes are difficult to separate fromthe other reaction products and purify.

[0005] An improved method of producing single-wall nanotubes isdescribed in U.S. Ser. No. 08/687,665, entitled “Ropes of Single-WalledCarbon Nanotubes” incorporated herein by reference in its entirety. Thismethod uses, inter alia, laser vaporization of a graphite substratedoped with transition metal atoms, preferably nickel, cobalt, or amixture thereof, to produce single-wall carbon nanotubes in yields of atleast 50% of the condensed carbon. The single-wall nanotubes produced bythis method tend to be formed in clusters, termed “ropes,” of 10 to 1000single-wall carbon nanotubes in parallel alignment, held together by vander Waals forces in a closely packed triangular lattice. Nanotubesproduced by this method vary in structure, although one structure tendsto predominate.

[0006] Although the laser vaporization process produces improvedsingle-wall nanotube preparations, the product is still heterogeneous,and the nanotubes are too tangled for many potential uses of thesematerials. In addition, the vaporization of carbon is a high energyprocess and is inherently costly. Therefore, there remains a need forimproved methods of producing single-wall nanotubes of greater purityand homogeneity. Furthermore, many practical materials could make use ofthe properties of single-wall carbon nanotubes if only they wereavailable as macroscopic components. However, such components have notbeen produced up to now.

SUMMARY OF THE INVENTION

[0007] Accordingly, it is an object of this invention to provide a highyield, single step method for producing large quantities of continuousmacroscopic carbon fiber from single-wall carbon nanotubes usinginexpensive carbon feedstocks at moderate temperatures.

[0008] It is another object of this invention to provide macroscopiccarbon fiber made by such a method.

[0009] It is also an object of this invention to provide a moleculararray of purified single-wall carbon nanotubes for use as a template incontinuous growing of macroscopic carbon fiber.

[0010] It is another object of the present invention to provide a methodfor purifying single-wall carbon nanotubes from the amorphous carbon andother reaction products formed in methods for producing single-wallcarbon nanotubes (e.g., by carbon vaporization).

[0011] It is also an object of the present invention to provide a newclass of tubular carbon molecules, optionally derivatized with one ormore functional groups, which are substantially free of amorphouscarbon.

[0012] It is also an object of this invention to provide a number ofdevices employing the carbon fibers, nanotube molecular arrays andtubular carbon molecules of this invention.

[0013] It is an object of this invention to provide composite materialcontaining carbon nanotubes.

[0014] It is another object of this invention to provide a compositematerial that is resistant to delamination.

[0015] A method for purifing a mixture comprising single-wall carbonnanotubes and amorphous carbon contaminate is disclosed. The methodincludes the steps of heating the mixture under oxidizing conditionssufficient to remove the amorphous carbon, followed by recovering aproduct comprising at least about 80% by weight of single-wall carbonnanotubes.

[0016] In another embodiment, a method for producing tubular carbonmolecules of about 5 to 500 nm in length is also disclosed. The methodincludes the steps of cutting single-wall nanotube containing-materialto form a mixture of tubular carbon molecules having lengths in therange of 5-500 nm and isolating a fraction of the molecules havingsubstantially equal lengths. The nanotubes disclosed may be used,singularly or in multiples, in power transmission cables, in solarcells, in batteries, as antennas, as molecular electronics, as probesand manipulators, and in composites.

[0017] In another embodiment, a method for forming a macroscopicmolecular array of tubular carbon molecules is disclosed. This methodincludes the steps of providing at least about 10⁶ tubular carbonmolecules of substantially similar length in the range of 50 to 500 nm;introducing a linking moiety onto at least one end of the tubular carbonmolecules; providing a substrate coated with a material to which thelinking moiety will attach; and contacting the tubular carbon moleculescontaining a linking moiety with the substrate.

[0018] In another embodiment, another method for forming a macroscopicmolecular array of tubular carbon molecules is disclosed. First, ananoscale array of microwells is provided on a substrate. Next, a metalcatalyst is deposited in each microwells. Next, a stream of hydrocarbonor CO feedstock gas is directed at the substrate under conditions thateffect growth of single-wall carbon nanotubes from each microwell.

[0019] In another embodiment, still another method for forming amacroscopic molecular array of tubular carbon molecules is disclosed. Itincludes the steps of providing surface containing purified butentangled and relatively endless single-wall carbon nanotube material;subjecting the surface to oxidizing condutions sufficient to cause shortlengths of broken nanotubes to protrude up from the surface; andapplying an electric field to the surface to cause the nanotubesprotruding from the surface to align in an orientation generallyperpendicular to the surface and coalesce into an array by van der Waalsinteraction forces.

[0020] In another embodiment, a method for continuously growing amacroscopic carbon fiber comprising at least about 10⁶ single-wallnanotubes in generally parallel orientation is disclosed. In thismethod, a macroscopic molecular array of at least about 10⁶ tubularcarbon molecules in generally parallel orientation and havingsubstantially similar lengths in the range of from about 50 to about 500nanometers is provided. The hemispheric fullerene cap is removed fromthe upper ends of the tubular carbon molecules in the array The upperends of the tubular carbon molecules in the array are then contactedwith a catalytic metal. A gaseous source of carbon is supplied to theend of the array while localized energy is applied to the end of thearray in order to heat the end to a temperature in the range of about500° C. to about 1300° C. The growing carbon fiber is continuouslyrecovered.

[0021] In another embodiment, a macroscopic molecular array comprisingat least about 10⁶ single-wall carbon nanotubes in generally parallelorientation and having substantially similar lengths in the range offrom about 5 to about 500 nanometers is disclosed.

[0022] In another embodiment, a composition of matter comprising atleast about 80% by weight of single-wall carbon nanotubes is disclosed.

[0023] In still another embodiment, macroscopic carbon fiber comprisingat least about 10⁶ single-wall carbon nanotubes in generally parallelorientation is disclosed.

[0024] In another embodiment, an apparatus for forming a continuousmacroscopic carbon fiber from a macroscopic molecular template arraycomprising at least about 10⁶ single-wall carbon nanotubes having acatalytic metal deposited on the open ends of said nanotubes isdisclosed. This apparatus includes a means for locally heating only theopen ends of the nanotubes in the template array in a growth andannealing zone to a temperature in the range of about 500° C. to about1300° C. It also includes a means for supplying a carbon-containingfeedstock gas to the growth and annealing zone immediately adjacent theheated open ends of the nanotubes in the template array. It alsoincludes a means for continuously removing growing carbon fiber from thegrowth and annealing zone while maintaining the growing open end of thefiber in the growth and annealing zone.

[0025] In another embodiment, a composite material containing nanotubesis disclosed. This composite material includes a matrix and a carbonnanotube material embedded within said matrix.

[0026] In another embodiment, a method of producing a composite materialcontaining carbon nanotube material is disclosed. It includes the stepsof preparing an assembly of a fibrous material; adding the carbonnanotube material to the fibrous material; and adding a matrix materialprecursor to the carbon nanotube material and the fibrous material.

[0027] In another embodiment a three-dimensional structure ofderivatized single-wall nanotube molecules that spontaneously form isdisclosed. It includes several component molecule having multiplederivatives brought together to assemble into the three-dimensionalstructure.

[0028] The foregoing objectives and others apparent to those skilled inthe art, are achieved according to the present invention as describedand claimed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a diagram of an apparatus for practicing the invention.

[0030]FIG. 2 is a diagram of an apparatus for practicing the inventionutilizing two different laser pulses to vaporize the composite rodtarget.

[0031]FIG. 3A is a TEM spectrum of purified SWNTs according to thepresent invention.

[0032]FIG. 3B is a SEM spectrum of purified SWNTs according to thepresent invention.

[0033]FIG. 3C is a Raman spectrum of purified SWNTs according to thepresent invention.

[0034]FIG. 4 is a schematic representation of a portion of anhomogeneous SWNT molecular array according to the present invention.

[0035]FIG. 5 is a schematic representation of an heterogeneous SWNTmolecular array according to the present invention.

[0036]FIG. 6 is a schematic representation of the growth chamber of thefiber apparatus according to the present invention.

[0037]FIG. 7 is a schematic representation of the pressure equalizationand collection zone of the fiber apparatus according to the presentinvention.

[0038]FIG. 8 is a composite array according to the present invention.

[0039]FIG. 9 is a composite array according to the present invention.

[0040]FIG. 10 is a power transmission cable according to the presentinvention.

[0041]FIG. 11 is a schematic representation of a bistable, nonvolatilenanoscale memory device according to the present invention.

[0042]FIG. 12 is a graph showing the energy wells that correspond toeach of the bistable states in the memory bit of FIG. 11.

[0043]FIG. 13 is a schematic representation of a lithium ion secondarybattery according to the present invention.

[0044]FIG. 14 is an anode for a lithium ion battery according to thepresent invention.

[0045]FIG. 15A is a medium-magnification transmission electronmicroscope image of single-wall nanotubes.

[0046]FIG. 15B is a high-magnification image of adjacent single-wallcarbon nanotubes.

[0047]FIG. 15C is a high-magnification image of adjacent single-wallcarbon nanotubes.

[0048]FIG. 15D is a high-magnification image of adjacent single-wallcarbon nanotubes.

[0049]FIG. 15E is a high-magnification image of the cross-section ofseven adjacent single-wall carbon nanotubes.

[0050]FIG. 16A is a scanning electron microscope (SEM) image of rawsingle-walled fullerene nanotube felt.

[0051]FIG. 16B is a SEM image of the single-walled fullerene nanotubefelt material of FIG. 16A after purification.

[0052]FIG. 16C is a SEM image of the single-walled fullerene nanotubefelt after tearing, resulting in substantial alignment of thesingle-walled nanotube rope fibers.

[0053]FIG. 17 is an atomic force microscopy image of cut fullerenenanotubes deposited on highly oriented pyrolytic graphite.

[0054]FIG. 18A is a graph of field flow fractionation (FFF) of a cutnanotubes suspension.

[0055]FIG. 18B represents the distribution of fullerene nanotubeslengths measured by AFM on three collections.

[0056]FIG. 19 shows an AFM image of a fullerene nanotube “pipe” tetheredto two 10 nm gold spheres.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] Carbon has from its very essence not only the propensity toself-assemble from a high temperature vapor to form perfect spheroidalclosed cages (of which C₆₀ is prototypical), but also (with the aid of atransition metal catalyst) to assemble into perfect single-wallcylindrical tubes which may be sealed perfectly at both ends with asemifullerene dome. These tubes, which may be thought of asone-dimensional single crystals of carbon, are true fullerene molecules,having no dangling bonds.

[0058] Single-wall carbon nanotubes of this invention are much morelikely to be free of defects than multi-wall carbon nanotubes. Defectsin single-wall carbon nanotubes are less likely than defects inmulti-walled carbon nanotubes because the latter can survive occasionaldefects, while the former have no neighboring walls to compensate fordefects by forming bridges between unsaturated carbon valances. Sincesingle-wall carbon nanotubes will have fewer defects, they are stronger,more conductive, and therefore more useful than multi-wall carbonnanotubes of similar diameter.

[0059] Carbon nanotubes, and in particular the single-wall carbonnanotubes of this invention, are useful for making electrical connectorsin micro devices such as integrated circuits or in semiconductor chipsused in computers because of the electrical conductivity and small sizeof the carbon nanotube. The carbon nanotubes are useful as antennas atoptical frequencies, and as probes for scanning probe microscopy such asare used in scanning tunneling microscopes (STM) and atomic forcemicroscopes (AFM). The carbon nanotubes may be used in place of or inconjunction with carbon black in tires for motor vehicles. The carbonnanotubes are also useful as supports for catalysts used in industrialand chemical processes such as hydrogenation, reforming and crackingcatalysts.

[0060] Ropes of single-wall carbon nanotubes made by this invention aremetallic, i.e., they will conduct electrical charges with a relativelylow resistance. Ropes are useful in any application where an electricalconductor is needed, for example as an additive in electricallyconductive paints or in polymer coatings or as the probing tip of anSTM.

[0061] In defining carbon nanotubes, it is helpful to use a recognizedsystem of nomenclature. In this application, the carbon nanotubenomenclature described by M. S. Dresselhaus, G. Dresselhaus, and P. C.Eklund, Science of Fullerness and Carbon Nanotubes, Chap. 19, especiallypp. 756-760, (1996), published by Academic Press, 525 B Street, Suite1900, San Diego, Calif. 92101-4495 or 6277 Sea Harbor Drive, Orlando,Fla. 32877 (ISBN 0-12-221820-5), which is hereby incorporated byreference, will be used. The single wall tubular fullerenes aredistinguished from each other by double index (n,m) where n and m areintegers that describe how to cut a single strip of hexagonal“chicken-wire” graphite so that it makes the tube perfectly when it iswrapped onto the surface of a cylinder and the edges are sealedtogether. When the two indices are the same, m=n, the resultant tube issaid to be of the “arm-chair” (or n,n) type, since when the tube is cutperpendicular to the tube axis, only the sides of the hexagons areexposed and their pattern around the periphery of the tube edgeresembles the arm and seat of an arm chair repeated n times. Arm-chairtubes are a preferred form of single-wall carbon nanotubes since theyare metallic, and have extremely high electrical and thermalconductivity. In addition, all single-wall nanotubes have extremely hightensile strength.

[0062] The dual laser pulse feature described herein produces anabundance of(10,10) single-wall carbon nanotubes. The (10,10),single-wall carbon nanotubes have an approximate tube diameter of 13.8Å±0.3 Å or 13.8 Å±0.2 Å.

[0063] The present invention provides a method for making single-wallcarbon nanotubes in which a laser beam vaporizes material from a targetcomprising, consisting essentially of, or consisting of a mixture ofcarbon and one or more Group VI or Group VIII transition metals. Thevapor from the target forms carbon nanotubes that are predominantlysingle-wall carbon nanotubes, and of those, the (10, 10) tube ispredominant. The method also produces significant amounts of single-wallcarbon nanotubes that are arranged as ropes, i.e., the single-wallcarbon nanotubes run parallel to each other. Again, the (10, 10) tube isthe predominant tube found in each rope. The laser vaporization methodprovides several advantages over the arc discharge method of makingcarbon nanotubes: laser vaporization allows much greater control overthe conditions favoring growth of single-wall carbon nanotubes, thelaser vaporization method permits continuous operation, and the laservaporization method produces single-wall carbon nanotubes in higheryield and of better quality. As described herein, the laser vaporizationmethod may also be used to produce longer carbon nanotubes and longerropes.

[0064] Carbon nanotubes may have diameters ranging from about 0.6nanometers (nm) for a single-wall carbon nanotube up to 3 nm, 5 nm, 10nm, 30 nm, 60 nm or 100 nm for single-wall or multi-wall carbonnanotubes. The carbon nanotubes may range in length from 50 nm up to 1millimeter (mm), 1 centimeter (cm), 3 cm, 5 cm, or greater. The yield ofsingle-wall carbon nanotubes in the product made by this invention isunusually high. Yields of single-wall carbon nanotubes greater than 10wt %, greater than 30 wt % and greater than 50 wt % of the materialvaporized are possible with this invention.

[0065] As will be described further, the one or more Group VI or VIIItransition metals catalyze the growth in length of a carbon nanotubeand/or the ropes. The one or more Group VI or VIII transition metalsalso selectively produce single-wall carbon nanotubes and ropes ofsingle-wall carbon nanotubes in high yield. The mechanism by which thegrowth in the carbon nanotube and/or rope is accomplished is notcompletely understood. However, it appears that the presence of the oneor more Group VI or VIII transition metals on the end of the carbonnanotube facilitates the addition of carbon from the carbon vapor to thesolid structure that forms the carbon nanotube. Applicants believe thismechanism is responsible for the high yield and selectivity ofsingle-wall carbon nanotubes and/or ropes in the product and willdescribe the invention utilizing this mechanism as merely an explanationof the results of the invention. Even if the mechanism is provedpartially or wholly incorrect, the invention which achieves theseresults is still fully described herein.

[0066] One aspect of the invention comprises a method of making carbonnanotubes and/or ropes of carbon nanotubes which comprises supplyingcarbon vapor to the live end of a carbon nanotube while maintaining thelive end of a carbon nanotube in an annealing zone. Carbon can bevaporized in accordance with this invention by an apparatus in which alaser beam impinges on a target comprising carbon that is maintained ina heated zone. A similar apparatus has been described in the literature,for example, in U.S. Pat. No. 5,300,203 which is incorporated herein byreference, and in Chai, et al., “Fullerenes with Metals Inside,” J Phys.Chem., vol. 95, no. 20, p. 7564 (1991).

[0067] Carbon nanotubes having at least one live end are formed when thetarget also comprises a Group VI or VIII transition metal or mixtures oftwo or more Group VI or VIII transition metals. In this application, theterm “live end” of a carbon nanotube refers to the end of the carbonnanotube on which atoms of the one or more Group VI or VIII transitionmetals are located. One or both ends of the nanotube may be a live end.A carbon nanotube having a live end is initially produced in the laservaporization apparatus of this invention by using a laser beam tovaporize material from a target comprising carbon and one or more GroupVI or VIII transition metals and then introducing the carbon/Group VI orVIII transition metal vapor to an annealing zone. Optionally, a secondlaser beam is used to assist in vaporizing carbon from the target. Acarbon nanotube having a live end will form in the annealing zone andthen grow in length by the catalytic addition of carbon from the vaporto the live end of the carbon nanotube. Additional carbon vapor is thensupplied to the live end of a carbon nanotube to increase the length ofthe carbon nanotube.

[0068] The carbon nanotube that is formed is not always a single-wallcarbon nanotube; it may be a multi-wall carbon nanotube having two,five, ten or any greater number of walls (concentric carbon nanotubes).Preferably, though, the carbon nanotube is a single-wall carbon nanotubeand this invention provides a way of selectively producing (10, 10)single-wall carbon nanotubes in greater and sometimes far greaterabundance than multi-wall carbon nanotubes.

[0069] The annealing zone where the live end of the carbon nanotube isinitially formed should be maintained at a temperature of 500° to 1500°C., more preferably 1000° to 1400° C. and most preferably 1100 to 1300°C. In embodiments of this invention where carbon nanotubes having liveends are caught and maintained in an annealing zone and grown in lengthby further addition of carbon (without the necessity of adding furtherGroup VI or VIII transition metal vapor), the annealing zone may becooler, 400° to 1500° C., preferably 400° to 1200° C. most preferably500° to 700° C. The pressure in the annealing zone should be maintainedin the range of 50 to 2000 Torr., more preferably 100 to 800 Torr. andmost preferably 300 to 600 Torr. The atmosphere in the annealing zonewill comprise carbon. Normally, the atmosphere in the annealing zonewill also comprise a gas that sweeps the carbon vapor through theannealing zone to a collection zone. Any gas that does not prevent theformation of carbon nanotubes will work as the sweep gas, but preferablythe sweep gas is an inert gas such as helium, neon, argon, krypton,xenon, radon, or mixtures of two or more of these. Helium and Argon aremost preferred. The use of a flowing inert gas provides the ability tocontrol temperature, and more importantly, provides the ability totransport carbon to the live end of the carbon nanotube. In someembodiments of the invention, when other materials are being vaporizedalong with carbon, for example one or more Group VI or VIII transitionmetals, those compounds and vapors of those compounds will also bepresent in the atmosphere of the annealing zone. If a pure metal isused, the resulting vapor will comprise the metal. If a metal oxide isused, the resulting vapor will comprise the metal and ions or moleculesof oxygen.

[0070] It is important to avoid the presence of too many materials thatkill or significantly decrease the catalytic activity of the one or moreGroup VI or VIII transition metals at the live end of the carbonnanotube. It is known that the presence of too much water (H₂O) and/oroxygen (O₂) will kill or significantly decrease the catalytic activityof the one or more Group VI or VIII transition metals. Therefore, waterand oxygen are preferably excluded from the atmosphere in the annealingzone. Ordinarily, the use of a sweep gas having less than 5 wt %, morepreferably less than 1 wt % water and oxygen will be sufficient. Mostpreferably the water and oxygen will be less than 0.1 wt %.

[0071] Preferably, the formation of the carbon nanotube having a liveend and the subsequent addition of carbon vapor to the carbon nanotubeare all accomplished in the same apparatus. Preferably, the apparatuscomprises a laser that is aimed at a target comprising carbon and one ormore Group VI or VIII transition metals, and the target and theannealing zone are maintained at the appropriate temperature, forexample by maintaining the annealing zone in an oven. A laser beam maybe aimed to impinge on a target comprising carbon and one or more GroupVI or VIII transition metals where the target is mounted inside a quartztube that is in turn maintained within a furnace maintained at theappropriate temperature. As noted above, the oven temperature is mostpreferably within the range of 1100° to 1300° C. The tube need notnecessarily be a quartz tube; it may be made from any material that canwithstand the temperatures (1000° to 1500° C.). Alumina or tungstencould be used to make the tube in addition to quartz.

[0072] Improved results are obtained where a second laser is also aimedat the target and both lasers are timed to deliver pulses of laserenergy at separate times. For example, the first laser may deliver apulse intense enough to vaporize material from the surface of thetarget. Typically, the pulse from the first laser will last about 10nanoseconds (ns). After the first pulse has stopped, a pulse from asecond laser hits the target or the carbon vapor or plasma created bythe first pulse to provide more uniform and continued vaporization ofmaterial from the surface of the target. The second laser pulse may bethe same intensity as the first pulse, or less intense, but the pulsefrom the second laser is typically more intense than the pulse from thefirst laser, and typically delayed about 20 to 60 ns, more preferably 40to 55 ns, after the end of the first pulse.

[0073] Examples of a typical specification for the first and secondlasers are given in Examples 1 and 3, respectively. As a rough guide,the first laser may vary in wavelength from 11 to 0.1 micrometers, inenergy from 0.05 to 1 Joule and in repetition frequency from 0.01 to1000 Hertz (Hz). The duration of the first laser pulse may vary from10⁻¹³ to 10⁻⁶ seconds (s). The second laser may vary in wavelength from11 to 0.1 micrometers, in energy from 0.05 to 1 Joule and in repetitionfrequency from 0.01 to 1000 Hertz. The duration of the second laserpulse may vary from 10⁻¹³ s to 10⁻⁶ s. The beginning of the second laserpulse should be separated from end of the first laser pulse by about 10to 100 ns. If the laser supplying the second pulse is an ultraviolet(UV) laser (an Excimer laser for example), the time delay can be longer,up to 1 to 10 milliseconds. But if the second pulse is from a visible orinfrared (IR) laser, then the adsorption is preferably into theelectrons in the plasma created by the first pulse. In this case, theoptimum time delay between pulses is about 20 to 60 ns, more preferably40 to 55 ns and most preferably 40 to 50 ns. These ranges on the firstand second lasers are for beams focused to a spot on the targetcomposite rod of about 0.3 to 10 mm diameter. The time delay en thefirst and second laser pulses is accomplished by computer control thatis known in the art of utilizing pulsed lasers. Applicants have used aCAMAC crate from LeCroy Research Systems, 700 Chestnut Ridge Road,Chestnut Ridge, N.Y. 10977-6499 along with a timing pulse generator fromKinetics Systems Corporation, 11 Maryknoll Drive, Lockport, Ill. 60441and a nanopulser from LeCroy Research Systems. Multiple first lasers andmultiple second lasers may be needed for scale up to larger targets ormore powerful lasers may be used. The main feature of multiple lasers isthat the first laser should evenly ablate material from the targetsurface into a vapor or plasma and the second laser should depositenough energy into the ablated material in the vapor or plasma plumemade by the first pulse to insure that the material is vaporized intoatoms or small molecules (less than ten carbon atoms per molecule). Ifthe second laser pulse arrives too soon after the first pulse, theplasma created by the first pulse may be so dense that the second laserpulse is reflected by the plasma. If the second laser pulse arrives toolate after the first pulse, the plasma and/or ablated material createdby the first laser pulse will strike the surface of the target. But ifthe second laser pulse is timed to arrive just after the plasma and/orablated material has been formed, as described herein, then the plasmaand/or ablated material will absorb energy from the second laser pulse.Also, it should be noted that the sequence of a first laser pulsefollowed by a second laser pulse will be repeated at the same repetitionfrequency as the first and second laser pulses, i.e., 0.01 to 1000 Hz.

[0074] In addition to lasers described in the Examples, other examplesof lasers useful in this invention include an XeF (365 nm wavelength)laser, an XeCl (308 nm wavelength) laser, a KrF (248 nm wavelength)laser or an ArF (193 nm wavelength) laser.

[0075] Optionally, but preferably, a sweep gas is introduced to the tubeupstream of the target and flows past the target carrying vapor from thetarget downstream. The quartz tube should be maintained at conditions sothat the carbon vapor and the one or more Group VI or VIII transitionmetals will form carbon nanotubes at a point downstream of the carbontarget but still within the heated portion of the quartz tube.Collection of the carbon nanotubes that form in the annealing zone maybe facilitated by maintaining a cooled collector in the internal portionof the far downstream end of the quartz tube. For example, carbonnanotubes may be collected on a water cooled metal structure mounted inthe center of the quartz tube. The carbon nanotubes will collect wherethe conditions are appropriate, preferably on the water cooledcollector.

[0076] Any Group VI or VIII transition metal may be used as the one ormore Group VI or VIII transition metals in this invention. Group VItransition metals are chromium (Cr), molybdenum (Mo), and tungsten (W).Group VIII transition metals are iron (Fe), cobalt (Co), nickel (Ni),ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), Iridium (Ir)and platinum (Pt). Preferably, the one or more Group VIII transitionmetals are selected from the group consisting of iron, cobalt,ruthenium, nickel and platinum. Most preferably, mixtures of cobalt andnickel or mixtures of cobalt and platinum are used. The one or moreGroup VI or VIII transition metals useful in this invention may be usedas pure metal, oxides of metals, carbides of metals, nitrate salts ofmetals, or other compounds containing the Group VI or VIII transitionmetal. Preferably, the one or more Group VI or VIII transition metalsare used as pure metals, oxides of metals, or nitrate salts of metals.The amount of the one or more Group VI or VIII transition metals thatshould be combined with carbon to facilitate production of carbonnanotubes having a live end, is from 0.1 to 10 atom percent, morepreferably 0.5 to 5 atom percent and most preferably 0.5 to 1.5 atompercent. In this application, atom percent means the percentage ofspecified atoms in relation to the total number of atoms present. Forexample, a 1 atom % mixture of nickel and carbon means that of the totalnumber of atoms of nickel plus carbon, 1% are nickel (and the other 99%are carbon). When mixtures of two or more Group VI or VIII transitionmetals are used, each metal should be 1 to 99 atom % of the metal mix,preferably 10 to 90 atom % of the metal mix and most preferably 20 to 80atom % of the metal mix. When two Group VI or VIII transition metals areused, each metal is most preferably 30 to 70 atom % of the metal mix.When three Group VI or VIII transition metals are used, each metal ismost preferably 20 to 40 atom % of the metal mix.

[0077] The one or more Group VI or VIII transition metals should becombined with carbon to form a target for vaporization by a laser asdescribed herein. The remainder of the target should be carbon and mayinclude carbon in the graphitic form, carbon in the fullerene form,carbon in the diamond form, or carbon in compound form such as polymersor hydrocarbons, or mixtures of two or more of these. Most preferably,the carbon used to make the target is graphite.

[0078] Carbon is mixed with the one or more Group VI or VIII transitionmetals in the ratios specified and then, in the laser vaporizationmethod, combined to form a target that comprises the carbon and the oneor more Group VI or VIII transition metals. The target may be made byuniformly mixing carbon and the one or more Group VI or VIII transitionmetals with carbon cement at room temperature and then placing themixture in a mold. The mixture in the mold is then compressed and heatedto about 130° C. for about 4 or 5 hours while the epoxy resin of thecarbon cement cues. The compression pressure used should be sufficientto compress the mixture of graphite, one or more Group VI or VIIItransition metals and carbon cement into a molded form that does nothave voids so that the molded form will maintain structural integrity.The molded form is then carbonized by slowly heating it to a temperatureof 810° C. for about 8 hours under an atmosphere of flowing argon. Themolded and carbonized targets are then heated to about 1200° C. underflowing argon for about 12 hours prior to their use as a target togenerate a vapor comprising carbon and the one or more Group VI or VIIItransition metals.

[0079] The invention may be further understood by reference to FIG. 1which is a cross-section view of laser vaporization in an oven. A target10 is positioned within tube 12. The target 10 will comprise carbon andmay comprise one or more Group VI or VIII transition metals. Tube 12 ispositioned in oven 14 which comprises insulation 16 and heating elementzone 18. Corresponding portions of oven 14 are represented by insulation16′ and heating element zone 18′. Tube 12 is positioned in oven 14 sothat target 10 is within heating element zone 18.

[0080]FIG. 1 also shows water cooled collector 20 mounted inside tube 12at the downstream end 24 of tube 12. An inert gas such as argon orhelium may be introduced to the upstream end 22 of tube 12 so that flowis from the upstream end 22 of tube 12 to the downstream end 24. A laserbeam 26 is produced by a laser (not shown) focused on target 10. Inoperation, oven 14 is heated to the desired temperature, preferably1100° to 1300° C., usually about 1200° C. Argon is introduced to theupstream end 22 as a sweep gas. The argon may optionally be preheated toa desired temperature, which should be about the same as the temperatureof oven 14. Laser beam 26 strikes target 10 vaporizing material intarget 10. Vapor from target 10 is carried toward the downstream end 24by the flowing argon stream. If the target is comprised solely ofcarbon, the vapor formed will be a carbon vapor. If one or more Group VIor VIII transition metals are included as part of the target, the vaporwill comprise carbon and one or more Group VI or VIII transition metals.

[0081] The heat from the oven and the flowing argon maintain a certainzone within the inside of the tube as an annealing zone. The volumewithin tube 12 in the section marked 28 in FIG. 1 is the annealing zonewherein carbon vapor begins to condense and then actually condenses toform carbon nanotubes. The water cooled collector 20 may be maintainedat a temperature of 700° C. or lower, preferably 500° C. or lower on thesurface to collect carbon nanotubes that were formed in the annealingzone.

[0082] In one embodiment of the invention, carbon nanotubes having alive end can be caught or mounted on a tungsten wire in the annealingzone portion of tube 12. In this embodiment, it is not necessary tocontinue to produce a vapor having one or more Group VI or VIIItransition metals. In this case, target 10 may be switched to a targetthat comprises carbon but not any Group VI or VIII transition metal, andcarbon will be added to the live end of the carbon nanotube.

[0083] In another embodiment of the invention, when the target comprisesone or more Group VI or VIII transition metals, the vapor formed bylaser beam 26 will comprise carbon and the one or more Group VI or VIIItransition metals. That vapor will form carbon nanotubes in theannealing zone that will then be deposited on water cooled collector 20,preferably at tip 30 of water cooled collector 20. The presence of oneor more Group VI or VIII transition metals in the vapor along withcarbon in the vapor preferentially forms carbon nanotubes instead offullerenes, although some fullerenes and graphite will usually be formedas well. In the annealing zone, carbon from the vapor is selectivelyadded to the live end of the carbon nanotubes due to the catalyticeffect of the one or more Group VI or VIII transition metals present atthe live end of the carbon nanotubes.

[0084]FIG. 2 shows an optional embodiment of the invention that can beused to make longer carbon nanotubes wherein a tungsten wire 32 isstretched across the diameter of tube 12 downstream of target 10 butstill within the annealing zone. After laser beam pulses hit the target10 forming a carbon/Group VI or VIII transition metal vapor, carbonnanotubes having live ends will form in the vapor. Some of those carbonnanotubes will be caught on the tungsten wire and the live end will beaimed toward the downstream end 24 of tube 12. Additional carbon vaporwill make the carbon nanotube grow. Carbon nanotubes as long as theannealing zone of the apparatus can be made in this embodiment. In thisembodiment, it is possible to switch to an all carbon target afterinitial formation of the carbon nanotubes having a live end, because thevapor need only contain carbon at that point.

[0085]FIG. 2 also shows part of second laser beam 34 as it impacts ontarget 10. In practice, laser beam 26 and second laser beam 34 would beaimed at the same surface of target 10, but they would impact thatsurface at different times as described herein.

[0086] It is also possible to stop the laser or lasers altogether. Oncethe single-wall carbon nanotube having a live end is formed. the liveend will catalyze growth of the single-wall carbon nanotube at lowertemperatures and with other carbon sources. The carbon source can beswitched to fullerenes, that can be transported to the live end by theflowing sweep gas. The carbon source can be graphite particles carriedto the live end by the sweep gas. The carbon source can be a hydrocarbonthat is carried to the live end by a sweep gas or a hydrocarbon gas ormixture of hydrocarbon gasses introduced to tube 12 to flow past thelive end. Hydrocarbons useful include methane, ethane, propane, butane,ethylene, propylene, benzene, toluene or any other paraffinic, olefinic,cyclic or aromatic hydrocarbon, or any other hydrocarbon.

[0087] The annealing zone temperature in this embodiment can be lowerthan the annealing zone temperatures necessary to initially form thesingle-wall carbon nanotube having a live end. Annealing zonetemperatures can be in the range of 400° to 1500° C., preferably 400 to1200° C., most preferably 500° to 700° C. The lower temperatures areworkable because the Group VI or VIII transition metal(s) catalyze theaddition of carbon to the nanotube at these lower temperatures.

[0088] Measurements show that the single-wall carbon nanotubes in theropes have a diameter of 13.8Å±0.2Å. A (10, 10) single-wall carbonnanotube has a calculated diameter of about 13.6Å, and the measurementson the single-wall carbon nanotubes in the ropes proves they arepredominantly the (10, 10) tube. The number of single-wall carbonnanotubes in each rope may vary from about 5 to 5000, preferably about10 to 1000, or 50 to 1000, and most preferably about 100 to 500. Thediameters of the ropes range from about 20 to 200Å, more preferablyabout 50 to 200Å. The (10, 10) single-wall carbon nanotube predominatesthe tubes in the ropes made by this invention Ropes having greater than10%, greater than 30%, greater than 50%, greater than 75%, and evengreater than 90% (10, 10) single-wall carbon nanotubes have beenproduced. Ropes having greater than 50% greater than 75% and greaterthan 90% armchair (n, n) single-wall carbon nanotubes are also made byand are a part of this invention. The single-wall carbon nanotubes ineach rope are arranged to form a rope having a 2-D triangular latticehaving a lattice constant of about 17Å. Ropes of 0.1 up to 10, 100 or1,000 microns in length are made by the invention. The resistivity of arope made in accordance with this invention was measured to be 0.34 to1.0 micro ohms per meter at 27° C. proving that the ropes are metallic.

[0089] A “felt” of the ropes described above may also be produced. Theproduct material is collected as a tangled collection of ropes stucktogether in a mat referred to herein as a “felt.” The felt materialcollected from the inventive process has enough strength to withstandhandling, and it has been measured to be electrically conductive. Feltsof 10 mm², 100 mm², 1000 mm² or greater, are formed in the inventiveprocess.

[0090] One advantage of the single-wall carbon nanotubes produced withthe laser vaporization in an oven method is their cleanliness. Typicaldischarge arc-produced single-wall carbon nanotubes are covered with athick layer of amorphous carbon, perhaps limiting their usefulnesscompared to the clean bundles of single-wall carbon nanotubes producedby the laser vaporization method. Other advantages and features of theinvention are apparent from the disclosure. The invention may also beunderstood by reference to Guo et al., “Catalytic Growth OfSingle-Walled Nanotubes By Laser Vaporization,” Chem. Phys. Lett., Vol.243, pp. 49-54 (1995).

[0091] The advantages achieved by the dual pulsed lasers insure that thecarbon and metal go through the optimum annealing conditions. The duallaser pulse process achieves this by using time to separate the ablationfrom the further and full vaporization of the ablated material. Thesesame optimum conditions can be achieved by using solar energy tovaporize carbon and metals as described in U.S. application Ser. No.08/483,045 filed Jun. 7, 1995 which is incorporated herein by reference.Combining any of the Group VI or VIII transition metals in place of themetals disclosed in the Ser. No. 08/483,045 application will produce thesingle-wall carbon nanotubes and the ropes of this invention.

Purification of Single-Wall Nanotubes

[0092] Carbon nanotubes in material obtained according to any of theforegoing methods may be purified according to the methods of thisinvention. A mixture containing at least a portion of single-wallnanotubes (“SWNT”) may be prepared, for example, as described by Iijima,et al, or Bethune, et al. However, production methods which producesingle-wall nanotubes in relatively high yield are preferred. Inparticular, laser production methods such as those disclosed in U.S.Ser. No. 08/687,665, may produce up to 70% or more single-wallnanotubes, and the single-wall nanotubes are predominately of thearm-chair structure.

[0093] The product of a typical process for making mixtures containingsingle-wall carbon nanotubes is a tangled felt which can includedeposits of amorphous carbon, graphite, metal compounds (e.g., oxides),spherical fullerenes, catalyst particles (often coated with carbon orfullerenes) and possibly multi-wall carbon nanotubes. The single-wallcarbon nanotubes may be aggregated in “ropes” or bundles of essentiallyparallel nanotubes.

[0094] When material having a high proportion of single-wall nanotubesis purified as described herein, the preparation produced will beenriched in single-wall nanotubes, so that the single-wall nanotubes aresubstantially free of other material. In particular, single-wallnanotubes will make up at least 80% of the preparation, preferably atleast 90%, more preferably at least 95% and most preferably over 99% ofthe material in the purified preparation.

[0095] The purification process of the present invention comprisesheating the SWNT-containing felt under oxidizing conditions to removethe amorphous carbon deposits and other contamining materials. In apreferred mode of this purification procedure, the felt is heated in anaqueous solution of an inorganic oxidant, such as nitric acid, a mixtureof hydrogen peroxide and sulfuric acid, or potassium permanganate.Preferably, SWNT-containing felts are refluxed in an aqueous solution ofan oxidizing acid at a concentration high enough to etch away amorphouscarbon deposits within a practical time frame. but not so high that thesingle-wall carbon nanotube material will be etched to a significantdegree. Nitric acid at concentrations from 2.0 to 2.6 M have been foundto be suitable. At atmospheric pressure, the reflux temperature of suchan aqueous acid solution is about 120° C.

[0096] In a preferred process, the nanotube-containing felts can berefluxed in a nitric acid solution at a concentration of 2.6 M for 24hours. Purified nanotubes may be recovered from the oxidizing acid byfiltration through, e.g., a 5 micron pore size TEFLON filter, likeMillipore Type LS. Preferably, a second 24 hour period of refluxing in afresh nitric solution of the same concentration is employed followed byfiltration as described above.

[0097] Refluxing under acidic oxidizing conditions may result in theesterification of some of the nanotubes, or nanotube contaminants. Thecontaminating ester material may be removed by saponification, forexample, by using a saturated sodium hydroxide solution in ethanol atroom temperature for 12 hours. Other conditions suitable forsaponification of any ester linked polymers produced in the oxidizingacid treatment will be readily apparent to those skilled in the art.Typically the nanotube preparation will be neutralized after thesaponification step. Refluxing the nanotubes in 6 M aqueous hydrochloricacid for 12 hours has been found to be suitable for neutralization,although other suitable conditions will be apparent to the skilledartisan.

[0098] After oxidation, and optionally saponification andneutralization, the purified nanotubes may be collected by settling orfiltration preferably in the form of a thin mat of purified fibers madeof ropes or bundles of SWNTs, referred to hereinafter as “bucky paper.”In a typical example, filtration of the purified and neutralizednanotubes on a TEFLON membrane with 5 micron pore size produced a blackmat of purified nanotubes about 100 microns thick. The nanotubes in thebucky paper may be of varying lengths and may consists of individualnanotubes, or bundles or ropes of up to 10³ single-wall nanotubes, ormixtures of individual single-wall nanotubes and ropes of variousthicknesses. Alternatively, bucky paper may be made up of nanotubeswhich are homogeneous in length or diameter and/or molecular structuredue to fractionation as described hereinafter.

[0099] The purified nanotubes or bucky paper are finally dried, forexample, by baking at 850° C. in a hydrogen gas atmosphere, to producedry, purified nanotube preparations.

[0100] When laser-produced single-wall nanotube material, produced bythe two-laser method of U.S. Ser. No. 08/687,665, was subjectedrefluxing in 2.6 M aqueous nitric acid, with one solvent exchange,followed by sonication in saturated NaOH in ethanol at room temperaturefor 12 hours, then neutralization by refluxing in 6 M aqueous HCl for 12hours, removal from the aqueous medium and baking in a hydrogen gasatmosphere at 850 C. in 1 atm H₂ gas (flowing at 1-10 sccm through a 1″quartz tube) for 2 hours, detailed TEM, SEM and Raman spectralexamination showed it to be >99% pure, with the dominant impurity beinga few carbon-encapsulated Ni/Co particles. (See FIGS. 3A, 3B, 3C)

[0101] In another embodiment, a slightly basic solution (e.g., pH ofapproximately 8-12) may also be used in the saponification step. Theinitial cleaning in 2.6 M HNO₃ converts amorphous carbon in the rawmaterial to various sizes of linked polycyclic compounds, such as fulvicand humic acids, as well as larger polycyclic aromatics with variousfunctional groups around the periphery, especially the carboxylic acidgroups. The base solution ionizes most of the polycyclic compounds,making them more soluble in aqueous solution. In a preferred process,the nanotube containing felts are refluxed in 2-5 M HNO₃ for 6-15 hoursat approximately 110°-125° C. Purified nanotubes may be filtered andwashed with 10 mM NaOH solution on a 3 micron pore size TSTP Isoporefilter. Next, the filtered nanotubes polished by stirring them for 30minutes at 60° C. in a S/N (Sulfuric acid/Nitric acid) solution. In apreferred embodiment, this is a 3:1 by volume mixture of concentratedsulfuric acid and nitric acid. This step removes essentially all theremaining material from the tubes that is produced during the nitricacid treatment.

[0102] Once the polishing is complete, a four-fold dilution in water ismade, and the nanotubes are again filtered on the 3 micron pore sizeTSTP Isopore filter. The nanotubes are again washed with a 10 mM NaOHsolution. Finally, the nanotubes are stored in water, because drying thenanotubes makes it difficult to resuspend them.

[0103] The conditions may be further optimized for particular uses, butthis basic approach by refluxing in oxidizing acid has been shown to besuccessful. Purification according to this method will producesingle-wall nanotubes for use as catalysts, as components in compositematerials, or as a starting material in the production of tubular carbonmolecules and continuous macroscopic carbon fiber of single-wallnanotube molecules.

Single-Wall Carbon Nanotube Molecules

[0104] Single-wall carbon nanotubes produced by prior methods are solong and tangled that it is very difficult to purify them or manipulatethem. However, the present invention provides for cutting them intoshort enough lengths that they are no longer tangled and annealing theopen ends closed. The short, closed tubular carbon molecules may bepurified and sorted very readily using techniques that are similar tothose used to sort DNA or size polymers. Thus, this inventioneffectively provides a whole new class of tubular carbon molecules.

[0105] Preparation of homogeneous populations of short carbon nanotubemolecules may be accomplished by cutting and annealing (reclosing) thenanotube pieces followed by fractionation. The cutting and annealingprocesses may be carried out on a purified nanotube bucky paper, onfelts prior to purification of nanotubes or on any material thatcontains single-wall nanotubes. When the cutting and annealing processis performed on felts, it is preferably followed by oxidativepurification, and optionally saponification, to remove amorphous carbon.Preferably, the starting material for the cutting process is purifiedsingle-wall nanotubes, substantially free of other material.

[0106] The short nanotube pieces can be cut to a length or selected froma range of lengths, that facilitates their intended use. Forapplications involving the individual tubular molecules per se (e.g.,derivatives, nanoscale conductors in quantum devices. i.e., molecularwire), the length can be from just greater than the diameter of the tubeup to about 1,000 times the diameter of the tube. Typical tubularmolecules will be in the range of from about 5 to 1,000 nanometers orlonger. For making template arrays useful in growing carbon fibers ofSWNT as described below, lengths of from about 50 to 500 nm arepreferred.

[0107] Any method of cutting that achieves the desired length ofnanotube molecules without substantially affecting the structure of theremaining pieces can be employed. The preferred cutting method employsirradiation with high mass ions. In this method, a sample is subjectedto a fast ion beam, e.g., from a cyclotron, at energies of from about0.1 to 10 giga-electron volts. Suitable high mass ions include thoseover about 150 AMU's such as bismuth, gold, uranium and the like.

[0108] Preferably, populations of individual single-wall nanotubemolecules having homogeneous length are prepared starting with aheterogeneous bucky paper and cutting the nanotubes in the paper using agold (Au⁺³³) fast ion beam. In a typical procedure, the bucky paper(about 100 micron thick) is exposed to ⁻10¹² fast ions per cm², whichproduces severely damaged nanotubes in the paper, on average every 100nanometers along the length of the nanotubes. The fast ions createdamage to the bucky paper in a manner analogous to shooting 10-100 nmdiameter “bullet holes” through the sample. The damaged nanotubes thencan be annealed (closed) by heat sealing of the tubes at the point whereion damage occurred, thus producing a multiplicity of shorter nanotubemolecules. At these flux levels, the shorter tubular molecules producedwill have a random distribution of cut sizes with a length peak nearabout 100 nm. Suitable annealing conditions are well know in thefullerene art, such as for example, baking the tubes in vacuum or inertgas at 1200° C. for 1 hour.

[0109] The SWNTs may also be cut into shorter tubular molecules byintentionally incorporating defect-producing atoms into the structure ofthe SWNT during production. These defects can be exploited chemically(e.g., oxidatively attacked) to cut the SWNT into smaller pieces. Forexample, incorporation of 1 boron atom for every 1000 carbon atoms inthe original carbon vapor source can produce SWNTs with built-in weakspots for chemical attack.

[0110] Cutting may also be achieved by sonicating a suspension of SWNTsin a suitable medium such as liquid or molten hydrocarbons. One suchpreferred liquid is 1,2-dichloreothane. Any apparatus that producessuitable acoustic energy can be employed. One such apparatus is theCompact Cleaner (One Pint) manufactured by Cole-Parmer, Inc. This modeloperates at 40 KHz and has an output of 20 W. The soniation cuttingprocess should be continued at a sufficient energy input and for asufficient time to substantially reduce the lengths of tubes, ropes orcables present in the original suspension. Typically times of from about10 minutes to about 24 hours can be employed depending on the nature ofthe starting material and degree of length reduction sought.

[0111] In another embodiment, sonication may be used to create defectsalong the rope lengths, either by the high temperatures and pressurescreated in bubble collapse (−5000° C. and ˜1000 atm), or by the attackof free radicals produced by sonochemistry. These defects are attackedby S/N to cleanly cut the nanotube, exposing the tubes underneath formore damage and cutting. As the acid attacks the tube, the tube iscompletely cut open and slowly etches back, its open end being unable toreclose at the moderate temperature. In a preferred process, thenanotubes are bath sonocated while being stirred in 40-45° C. S/N for 24hours. Next, the nanotubes are stirred with no sonication in the S/N for2 hours at 40-45° C. This is to attack, with the S/N, all the defectscreated by the sonication without creating more defects. Then, thenanotubes are diluted four-fold with water, and then filtered using a0.1 micron pore size VCTP filter. Next, the nanotubes are filtered andwashed with a 10 mM NaOH solution on the VCTP filter. The nanotubes arepolished by stirring them for 30 minutes at 70° C. in a S/N solution.The polished nanotubes are diluted four-fold with water, filtered usingthe 0.1 micron pore size VCTP filters, then filtered and washed with 10mM NaOH on a 0.1 micron pore size VCTP filter, and then stored in water.

[0112] Oxidative etching e.g., with highly concentrated nitric acid, canalso be employed to effect cutting of SWNTs into shorter lengths. Forexample, refluxing SWNT material in concentrated HNO₃ for periods ofseveral hours to 1 or 2 days will result in significantly shorter SWNTs.The rate of cutting by this mechanism is dependent on the degree ofhelicity of the tubes. This fact may be utilized to facilitateseparation of tubes by type, i.e., (n,n) from (m,n).

[0113] Length distribution shortens systematically with exposure time tothe acid. For example, in a 3/1 concentrated sulfuric/nitric acid at 70°C. the average cut nanotube shortens at a rate of approximately 100 nmhr⁻¹. In a 4/1 sulfuric acid/30% aqueous hydrogen peroxide (“piranha”)mixture at 70° C., the shortening rate is approximately 200 nm hr⁻¹. Theetching rate is sensitive to the chrial index of the nanotubes (n,m),with all “arm-chair” tubes (m=x) having a distinct chemistry from the“zig-zag” tubes (m=0), and to a lesser extend with tubes of intermediatehelical angle (n≠m).

[0114] The cleaned nanotube material may be cut into 50-500 nm lengths,preferably 100-300 nm lengths, by this process. The resulting pieces mayform a colloidal suspension in water when mixed with a surfactant suchas Triton X-100™ (Aldrich, Milwaukee, Wis.). These sable suspensionspermit a variety of manipulations such as sorting by length using fieldflow fractionation, and electrodeposition on graphite followed by AFMimaging.

[0115] In another embodiment, SWNTs can be cut using electron beamcutting apparatus in the known manner.

[0116] Combination of the foregoing cutting techniques can also beemployed.

[0117] Homogeneous populations of single-walled nanotubes may beprepared by fractionating heterogeneous nanotube populations afterannealing. The annealed nanotubes may be disbursed in an aqueousdetergent solution or an organic solvent for the fractionation.Preferably the tubes will be disbursed by sonication in benzene,toluene, xylene or molten naphthalene. The primary function of thisprocedure is to separate nanotubes that are held together in the form ofropes or mats by van der Waals forces. Following separation intoindividual nanotubes, the nanotubes may be fractionated by size by usingfractionation procedures which are well known, such as procedures forfractionating DNA or polymer fractionation procedures. Fractionationalso can be performed on tubes before annealing, particularly if theopen ends have substituents (carboxy, hydroxy, etc.), that facilitatethe fractionation either by size or by type. Alternatively, the closedtubes can be opened and derivatized to provide such substituents. Closedtubes can also be derivatized to facilitate fractionation, for example,by adding solubilizing moieties to the end caps.

[0118] Electrophoresis is one such technique well suited tofractionation of SWNT molecules since they can easily be negativelycharged. It is also possible to take advantage of the differentpolarization and electrical properties of SWNTs having differentstructure types (e.g., arm chair and zig-zag) to separate the nanotubesby type. Separation by type can also be facilitated by derivatizing themixture of molecules with a moiety that preferentially bonds to one typeof structure.

[0119] In a typical example, a 100 micron thick mat of black buckypaper, made of nanotubes purified by refluxing in nitric acid for 48hours was exposed for 100 minutes to a 2 GeV beam of gold (Au⁺³³) ionsin the Texas A&M Superconducting Cyclotron Facility (net flux of up to10¹² ions per cm²). The irradiated paper was baked in a vacuum at 1200°C. for 1 hr to seal off the tubes at the “bullet holes,” and thendispersed in toluene while sonicating. The resultant tubular moleculeswere examined via SEM, AFM and TEM.

[0120] The procedures described herein produce tubular molecules thatare single-wall nanotubes in which the cylindrical portion is formedfrom a substantially defect-free sheet of graphene (carbon in the formof attached hexagons) rolled up and joined at the two edges parallel toits long axis. The nanotube can have a fullerene cap (e.g., hemispheric)at one end of the cylinder and a similar fullerene cap at the other end.One or both ends can also be open. Prepared as described herein, theseSWNT molecules are substantially free of amorphous carbon. Thesepurified nanotubes are effectively a whole new class of tubularmolecules.

[0121] In general the length, diameter and helicity of these moleculescan be controlled to any desired value. Preferred lengths are up to 10⁶hexagons; preferred diameters are about 5 to 50 hexagon circumference;and the preferred helical angle is 0° to 30°.

[0122] Preferably, the tubular molecules are produced by cutting andannealing nanotubes of predominately arm-chair (n,n) configuration,which may be obtained by purifying material produced according to themethods discussed above. These (n,n) carbon molecules, purified asdescribed herein, are the first truly “metallic molecules.” Thesemolecules are useful for making electrical connectors for devices suchas integrated circuits or semiconductor chips used in computers becauseof the high electrical conductivity and small size of the carbonmolecule. SWNT molecules are also useful as components of electricaldevices where quantum effects dominate at room temperatures, forexample, resonant tunneling diodes. The metallic carbon molecules areuseful as antennas at optical frequencies, and as probes for scanningprobe microscopy such as are used in scanning tunneling microscopes(STM) and atomic force microscopes (AFM). The semiconducting SWNTstructures, an (m, n) tube wherein m≠n may be used, with appropriatedoping, as nanoscale semiconductor devices such as transistors.

[0123] The tubular carbon molecules of this invention may also be usedin RF shielding applications, e.g., to make microwave absorbingmaterials.

[0124] Single-walled nanotube molecules may serve as catalysts in any ofthe reactions known to be catalyzed as fullerenes, with the addedbenefits that the linear geometry of the molecule provides. The carbonnanotubes are also useful as supports for catalysts used in industrialand chemical processes such as hydrogenation, reforming and crackingcatalysts. Materials including the SWNT molecules can also be used ashydrogen storage devices in battery and fuel cell devices.

[0125] The tubular carbon molecules produced according to this inventioncan be chemically derivatized at their ends (which may be made eitheropen or closed with a hemi-fullerene dome). Derivatization at thefullerene cap structures is facilitated by the well-known reactivity ofthese structures. See, “The Chemistry of Fullerenes” R. Taylor ed., Vol.4 of the advanced Series in Fullerenes, World Scientific Publishers,Singapore, 1995; A. Hirsch, “The Chemistry of the Fullerenes,” Thieme,1994. Alteratively, the fullerene caps of the single-walled nanotubesmay be removed at one or both ends of the tubes by short exposure tooxidizing conditions (e.g., with nitric acid or O₂/CO₂) sufficient toopen the tubes but not etch them back too far, and the resulting opentube ends maybe derivatized using known reaction schemes for thereactive sites at the graphene sheet edge.

[0126] In general, the structure of such molecules can be shown asfollows:

[0127] where

[0128] is a substantially defect-free cylindrical graphene sheet (whichoptionally can be doped with non-carbon atoms) having from about 10² toabout 10 ⁶ carbon atoms, and having a length of from about 5 to about1000 nm, preferably about 5 to about 500 nm;

[0129] is a fullerene cap that fits perfectly on the cylindricalgraphene sheet, has at least six pentagons and the remainder hexagonsand typically has at least about 30 carbon atoms;

[0130] n is a number from 0 to 30, preferably 0 to 12; and

[0131] R, R¹, R², R³, R⁴, and R⁵ each may be independently selected fromthe group consisting of hydrogen; alkyl, acyl aryl aralkyl, halogen;substituted or unsubstituted thiol; unsubstituted or substituted amino;hydroxy, and OR′ wherein R′ is selected from the group consisting ofhydrogen, alkyl, acyl, aryl aralkyl, unsubstituted of substituted amino;sunstituted or unsubstituted thiol; and halogen; and a linear or cycliccarbon chain optionally interrupted with one or more heteroatom, andoptionally substituted with one or more ═O, or ═S, hydroxy, anaminoalkyl group, an amino acid, or a peptide of 2-8 amino acids.

[0132] The following definitions are used herein.

[0133] The term “alkyl” as employed herein includes both straight andbranched chain radicals, for example methyl, ethyl, propyl, isopropyl,butyl, t-butyl, isobutyl, pentyl, hexyl, isohexyl, heptyl,4,4-dimethylpentyl, octyl, 2,2,4-trimethylpentyl, nonyl, decyl, undecyl,dodecyl, the various branched chain isomers thereof. The chain may belinear or cyclic, saturated or unsaturated, containing, for example,double and triple bonds. The alkyl chain may be interrupted orsubstituted with, for example, one or more halogen, oxygen, hydroxy,silyl, amino, or other acceptable substituents.

[0134] The term “acyl” as used herein refers to carbonyl groups of theformula —COR wherein R may be any suitable substituent such as, forexample, alkyl, aryl, aralkyl, halogen; substituted or unsubstitutedthiol; unsubstituted or substituted amino, unsubstituted or substitutedoxygen, hydroxy, or hydrogen.

[0135] The term “aryl” as employed herein refers to monocyclic, bicyclicor tricyclic aromatic groups containing from 6 to 14 carbons in the ringportion, such as phenyl, naphthyl, substituted phenyl, or substitutednaphthyl, wherein the substituent on either the phenyl or naphthyl maybe for example C₁₋₄ alkyl, halogen, C₁₋₄ alkoxy, hydroxy or nitro.

[0136] The term “aralkyl” as used herein refers to alkyl groups asdiscussed above having an aryl substituent, such as benzyl,p-nitrobenzyl, phenylethyl, diphenylmethyl, and triphenylmethyl.

[0137] The term “aromatic or non-aromatic ring” as used herein includes5-8 membered aromatic and non-aromatic rings uninterrupted orinterrupted with one or more heteroatom, for example O, S, SO, SO₂, andN, or the ring may be unsubstituted or substituted with, for example,halogen, alkyl, acyl, hydroxy, aryl, and amino, said heteroatom andsubstituent may also be substituted with, for example, alkyl, acyl,aryl, or aralkyl.

[0138] The term “linear or cyclic” when used herein includes, forexample, a linear chain which may optionally be interrupted by anaromatic or non-aromatic ring. Cyclic chain includes, for example, anaromatic or non-aromatic ring which may be connected to, for example, acarbon chain which either precedes or follows the ring.

[0139] The tern “substituted amino” as used herein refers to an aminowhich may be substituted with one or more substituent, for example,alkyl, acyl, aryl, aralkyl, hydroxy, and hydrogen.

[0140] The term “substituted thiol” as used herein refers to a thiolwhich may be substituted with one or more substituent, for example,alkyl, acyl, aryl, aralkyl, hydroxy, and hydrogen.

[0141] Typically, open ends may contain up to about 20 substituents andclosed ends may contain up to about 30 substituents. It is preferred,due to stearic hindrance, to employ up to about 12 substituents per end.

[0142] In addition to the above described external derivatization, theSWNT molecules of the present invention can be modified endohedrally,i.e., by including one or more metal atoms inside the structure, as isknown in the endohedral fullerene art. It is also possible to “load” theSWNT molecule with one or more smaller molecules that do not bond to thestructures, e.g., C₆₀, to permit molecular switching as the C₆₀ buckyball shuttles back and forth inside the SWNT molecule under theinfluence of external fields or forces.

[0143] To produce endohedral tubular carbon molecules, the internalspecies (e.g., metal atom, bucky ball molecules) can either beintroduced during the SWNT formation process or added after preparationof the tubular molecules. Incorporation of metals into the carbon sourcethat is evaporated to form the SWNT material is accomplished in themanner described in the prior art for making endohedralmetallofullerenes. Bucky balls, i.e., spheroidal fullerene molecules,are preferably loaded into the tubular carbon molecules of thisinvention by removing one or both end caps of the tubes employingoxidation etching described above, and adding an excess of bucky ballmolecules (e.g., C₆₀, C₇₀) by heating the mixture (e.g., from about 500to about 600° C.) in the presence of C₆₀ or C₇₀ containing vapor for anequilibration period (e.g., from about 12 to about 36 hours). Asignificant proportion (e.g., from a few tenths of a percent up to about50 percent or more) of the tubes will capture a bucky ball moleculeduring this treatment. By selecting the relative geometry of the tubeand ball this process can be facilitated. For example, C₆₀ and C₇₀ fitvery nicely in a tubular carbon molecule cut from a (10, 10) SWNT(I.D.≅1 nm). After the loading step, the tubes containing bucky ballmolecules can be closed (annealed shut) by heating under vacuum to about1100° C. Bucky ball encapsulation can be confirmed by microscopicexamination, e.g., by TEM.

[0144] Endohedrally loaded tubular carbon molecules can then beseparated from empty tubes and any remaining loading materials by takingadvantage of the new properties introduced into the loaded tubularmolecules, for example, where the metal atom imparts magnetic orparamagnetic properties to the tubes, or the bucky ball imparts extramass to the tubes. Separation and purification methods based on theseproperties and others will be readily apparent to those skilled in theart.

[0145] Fullerene molecules like C₆₀ or C₇₀ will remain inside theproperly selected tubular molecule (e.g., one based on (10,10) SWNTs)because from an electronic standpoint (e.g., by van der Waalsinteraction) the tube provides an environment with a more stable energyconfiguration than that available outside the tube.

Molecular Arrays of Single-Wall Carbon Nanotubes

[0146] An application of particular interest for a homogeneouspopulation of SWNT molecules is production of a substantiallytwo-dimensional array made up of single-walled nanotubes aggregating(e.g., by van der Waals forces) in substantially parallel orientation toform a monolayer extending in directions substantially perpendicular tothe orientation of the individual nanotubes. Such monolayer arrays canbe formed by conventional techniques employing “self-assembledmonolayers” (SAM) or Langmiur-Blodgett films, see Hirch, pp. 75-76. Sucha molecular array is illustrated schematically in FIG. 4. In thisfigure, nanotubes 1 are bound to a substrate 2 having a reactive coating3 (e.g., gold).

[0147] Typically, SAMs are created on a substrate which can be a metal(such as gold, mercury or ITO (indium—tin-oxide)). The molecules ofinterest, here the SWNT molecules, are linked (usually covalently) tothe substrate through a linker moiety such as —S—, —S—(CH₂)_(n)—NH—,—SiO₃(CH₂)₃NH— or the like. The linker moiety may be bound first to thesubstrate layer or first to the SWNT molecule (at an open or closed end)to provide for reactive self-assembly. Langmiur-Blodgett films areformed at the interface between two phases, e.g., a hydrocarbon (e.g.,benzene or toluene) and water. Orientation in the film is achieved byemploying molecules or linkers that have hydrophilic and lipophilicmoieties at opposite ends.

[0148] The configuration of the SWNT molecular array may be homogenousor heterogeneous depending on the use to which it will be put. UsingSWNT molecules of the same type and structure provides a homogeneousarray of the type shown in FIG. 4. By using different SWNT molecules,either a random or ordered heterogeneous structure can be produced. Anexample of an ordered heterogeneous array is shown in FIG. 5 where tubes4 are (n,n), i.e., metallic in structure and tubes 5 are (m,n), i.e.,insulating. This configuration can be achieved by employing successivereactions after removal of previously masked areas of the reactivesubstrate.

[0149] Arrays containing from 10³ up to 10¹⁰ and more SWNT molecules insubstanially parallel relationships can be used per se as a nanoporousconductive molecular membrane, e.g. for use in batteries such as thelithium ion battery. This membrane can also be used (with or withoutattachment of a photoactive molecule such as cis-(bisthiacyanato bis(4,4′-dicarboxy-2-2′-bipyridine Ru (II)) to produce a highly efficientphoto cell of the type shown in U.S. Pat. No. 5,084,365.

[0150] One preferred use of the SWNT molecular arrays of the presentinvention is to provide a “seed” or template for growth of macroscopiccarbon fiber of single-wall carbon nanotubes as described below. The useof a macroscopic cross section in this template is particularly usefulfor keeping the live (open) end of the nanotubes exposed to feedstockduring growth of the fiber. The template array of this invention can beused as formed on the original substrate, cleaved from its originalsubstrate and used with no substrate (the van der Waals forces will holdit together) or transferred to a second substrate more suitable for theconditions of fiber growth.

[0151] Where the SWNT molecular array is to be used as a seed ortemplate for growing macroscopic carbon fiber as described below, thearray need not be formed as a substantially two-dimensional array. Anyform of array that presents at its upper surface a two-dimensional arraycan be employed. In the preferred embodiment, the template moleculararray is a manipulatable length of macroscopic carbon fiber as producedbelow.

[0152] Another method for forming a suitable template molecular arrayinvolves employing purified bucky paper as the starting material. Uponoxidative treatment of the bucky paper surface (e.g., with O₂/CO₂ atabout 500° C.), the sides as well as ends of SWNTs are attacked and manytube and/or rope ends protrude up from the surface of the paper.Disposing the resulting bucky paper in an electric field (e.g., 100V/cm² results in the protruding tubes and or ropes aligning in adirection substantially perpendicular to the paper surface. These tubestend to coalesce due to van der Waals forces to form a molecular array.

[0153] Alternatively, a molecular array of SWNTs can be made by“combing” the purified bucky paper starting material. “Combing” involvesthe use of a sharp microscopic tip such as the silicon pyramid on thecantilever of a scanning force microscope (“SFM”) to align thenanotubes. Specifically, combing is the process whereby the tip of anSFM is systematically dipped into, dragged through, and raised up from asection of bucky paper. An entire segment of bucky paper could becombed, for example, by: (i) systematically dipping, dragging, raisingand moving forward an SFM tip along a section of the bucky paper, (ii)repeating the sequence in (i) until completion of a row; and (iii)repositioning the tip along another row and repeating (i) and (ii). In apreferred method of combing, the section of bucky paper of interest iscombed through as in steps (i)-(iii) above at a certain depth and thenthe entire process is repeated at another depth. For example, alithography script can be written and run which could draw twenty lineswith 0.5 μm spacing in a 10×10 μm square of bucky paper. The script canbe run seven times, changing the depth from zero to three μm in 0.5 μmincrements.

[0154] Large arrays (i.e.,>10⁶ tubes) also can be assembled usingnanoprobes by combining smaller arrays or by folding linear collectionsof tubes and/or ropes over (i.e., one folding of a collection of n tubesresults in a bundle with 2 n tubes).

[0155] Macroscopic arrays can also be formed by providing a nanoscalemicrowell structure (e.g., a SiO₂ coated silicon wafer with>10⁶rectangular 10 nm wide, 10 nm deep wells formed in the surface byelectron beam lithographic techniques). A suitable catalyst metal duster(or precursor) is deposited in each well and a carbon-containingfeedstock is directed towards the array under growth conditionsdescribed below to initiate growth of SWNT fibers from the wells.Catalysts in the form of preformed nanoparticles (i.e., a few nanometersin diameter) as described in Dai et al., “Single-Wall Nanotubes Producedby Metal-Catalyzed Disproportionation of Carbon Monoxide,” Chem. Phys.Lett. 260 (1996), 471-475 (“Dai”) can also be used in the wells. Anelectric field can be applied to orient the fibers in a directionsubstantially perpendicular to the wafer surface.

Growth of Continuous Carbon Fiber from SWNT Molecular Arrays

[0156] The present invention provides methods for growing continuouscarbon fiber from SWNT molecular arrays to any desired length. Thecarbon fiber which comprises an aggregation of substantially parallelcarbon nanotubes may be produced according to this invention by growth(elongation) of a suitable seed molecular array. The preferred SWNTmolecular array is produced as described above from a SAM of SWNTmolecules of substantially uniform length. As used herein, the term“macroscopic carbon fiber” refers to fibers having a diameter largeenough to be physically manipulated, typically greater than about 1micron and preferably greater than about 10 microns.

[0157] The first step in the growth process is to open the growth end ofthe SWNTs in the molecular array. This can be accomplished as describedabove with an oxidative treatment. Next, a transition metal catalyst isadded to the open-ended seed array. The transition metal catalyst can beany transition metal that will cause conversion of the carbon-containingfeedstock described below into highly mobile carbon radicals that canrearrange at the growing edge to the favored hexagon structure. Suitablematerials include transition metals, and particularly the Group VI orVIII transition metals, i.e., chromium (Cr), molybdenum (Mo), tungsten(W), iron (Fe), cobalt (Co), nickel (NI), ruthenium (Ru), rhodium (Rh),palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt). Metals fromthe lanthanide and actinide series may also be used. Preferred are Fe,Ni, Co and mixtures thereof. Most preferred is a 50/50 mixture (byweight) of Ni and Co.

[0158] The catalyst should be present on the open SWNT ends as a metalcluster containing from about 10 metal atoms up to about 200 metal atoms(depending on the SWNT molecule diameter). Typically, the reactionproceeds most efficiently if the catalyst metal cluster sits on top ofthe open tube and does not bridge over more than one or two tubes.Preferred are metal clusters having a cross-section equal to from about0.5 to about 1.0 times the tube diameter (e.g., about 0.7 to 1.5 nm).

[0159] In the preferred process, the catalyst is formed, in situ, on theopen tube ends of the molecular array by a vacuum deposition process.Any suitable equipment, such as that used in Molecular Beam Epitaxy(MBE) deposition, can be employed. One such device is a Küdsen EffusionSource Evaporator. It is also possible to effect sufficient depositionof metal by simply heating a wire in the vicinity of the tube ends(e.g., a Ni/CO wire or separate Ni and CO wires) to a temperature belowthe melting point at which enough atoms evaporate from one wire surface(e.g., from about 900 to about 1300° C.). The deposition is preferablycarried out in a vacuum with prior outgassing. Vacuums of about 10⁻⁶ to10⁻⁸ Torr are suitable. The evaporation temperature should be highenough to evaporate the metal catalyst. Typically, temperatures in therange of 1500 to 2000° C. are suitable for the Ni/Co catalyst of thepreferred embodiment. In the evaporation process, the metal is typicallydeposited as monolayers of metal atoms. From about 1-10 monolayers willgenerally give the required amount of catalyst. The deposition oftransition metal clusters on the open tube tops can also be accomplishedby laser vaporization of metal targets in a catalyst deposition zone.

[0160] The actual catalyst metal cluster formation at the open tube endsis carried out by heating the tube ends to a temperature high enough toprovide sufficient species mobility to permit the metal atoms to findthe open ends and assemble into clusters, but not so high as to effectclosure of the tube ends. Typically, temperatures of up to about 500° C.are suitable. Temperatures in the range of about 400-500° C. arepreferred for the Ni/Co catalysts system of one preferred embodiment.

[0161] In a preferred embodiment, the catalyst metal cluster isdeposited on the open nanotube end by a docking process that insuresoptimum location for the subsequent growth reaction. In this process,the metal atoms are supplied as described above, but the conditions aremodified to provide reductive conditions, e.g., at 800° C., 10 millitorof H₂ for 1 to 10 minutes. There conditions cause the metal atomclusters to migrate through the system in search of a reactive site.During the reductive heating the catalyst material will ultimataly findand settle on the open tube ends and begin to etch back the tube. Thereduction period should be long enough for the catalyst particles tofind and bed to etch back the nanotubes, but not so long as tosubstantially etch away the tubes. By changing to the above-describedgrowth conditions, the etch-back process is reversed. At this point, thecatalyst particles are optimally located with respect to the tube endssince they already were catalytically active at those sites (albeit inthe reverse process).

[0162] The catalyst can also be supplied in the form of catalystprecursors which convert to active form under growth conditions such asoxides, other salts or ligand stabilized metal complexes. As an example,transition metal complexes with alkylamines (primary, secondary ortertiary) can be employed. Similar alkylamine complexes of transitionmetal oxides also can be employed.

[0163] In an alternative embodiment, the catalyst may be supplied aspreformed nanoparticles (i.e., a few nanometers in diameter) asdescribed in Dai.

[0164] In the next step of the process of the present invention, theSWNT molecular array with catalyst deposited on the open tube ends issubjected to tube growth (extension) conditions. This may be in the sameapparatus in which the catalyst is deposited or a different apparatus.The apparatus for carrying out this process will require, at a minimum,a source of carbon-containing feedstock and a means for maintaining thegrowing end of the continuous fiber at a growth and annealingtemperature where carbon from the vapor can be added to the growing endsof the individual nanotubes under the direction of the transition metalcatalyst. Typically, the apparatus will also have means for continuouslycollecting the carbon fiber. The process will be described forillustration purposes with reference to the apparatus shown in FIGS. 6and 7.

[0165] The carbon supply necessary to grow the SWNT molecular array intoa continuous fiber is supplied to the reactor 10, in gaseous formthrough inlet 11. The gas stream should be directed towards the frontsurface of the growing array 12. The gaseous carbon-containing feedstockcan be any hydrocarbon or mixture of hydrocarbons including alkyls,acyls, aryls, aralkyls and the like, as defined above. Preferred arehydrocarbons having from about 1 to 7 carbon atoms. Particularlypreferred are methane, ethane, ethylene, actylene, acetone, propane,propylene and the like. Most preferred is ethylene. Carbon monoxide mayalso be used and in some reactions is preferred. Use of CO feedstockwith preformed Mo-based nano-catalysts is believed to follow a differentreaction mechanism than that proposed for in situ-formed catalystclusters. See Dai.

[0166] The feedstock concentration is preferably as chosen to maximizethe rate of reaction, with higher concentrations of hydrocarbon givingfaster growth rates. In general the partial pressure of the feedstockmaterial (e.g., ethylene) can be in the 0.001 to 1000.0 Torr range, withvalues in the range of about 1.0 to 10 Torr being preferred. The growthrate is also a function of the temperature of the growing array tip asdescribed below, and as a result growth temperatures and feed stockconcentration can be balanced to provide the desired growth rates.

[0167] It is not necessary or preferred to preheat the carbon feedstockgas, since unwanted pyrolysis at the reactor walls can be minimizedthereby. The only heat supplied for the growth reaction should befocused at the growing tip of the fiber 12. The rest of the fiber andthe reaction apparatus can be kept at room temperature. Heat can besupplied in a localized fashion by any suitable means. For small fibers(<1 mm in diameter), a laser 13 focused at the growing end is preferred(e.g., a C-W laser such as an argon ion laser beam at 514 nm). Forlarger fibers, heat can be supplied by microwave energy or R-F energy,again localized at the growing fiber tip. Any other form of concentratedelectromagnetic energy that can be focused on the growing tip can beemployed (e.g., solar energy). Care should be taken, however, to avoidelectromagnetic radiation that will be absorbed to any appreciableextent by the feedstock gas.

[0168] The SWNT molecular array tip should be heated to a temperaturesufficient to cause growth and efficient annealing of defects in thegrowing fiber, thus forming a growth and annealing zone at the tip. Ingeneral, the upper limit of this temperature is governed by the need toavoid pyrolysis of the feedstock and fouling of the reactor orevaporation of the deposited metal catalyst. For most feedstocks, thisis below about 1300° C. The lower end of the acceptable temperaturerange is typically about 500° C., depending on the feedstock andcatalytic efficiency. Preferred are in the range of about 500° C. toabout 1200° C. More preferred are temperatures in the range of fromabout 700° C. to about 1200° C. Temperatures in the range of about 900°C. to about 1100° C. are the most preferred, since at these temperaturesthe best annealing of defects occurs. The temperature at the growing endof the cable is preferably monitored by, and controlled in response to,an optical pyrometer 14, which measures the incandescence produced.While not preferred due to potential fouling problems, it is possibleunder some circumstances to employ an inert sweep gas such as argon orhelium.

[0169] In general, pressure in the growth chamber can be in the range of1 millitorr to about 1 atmosphere. The total pressure should be kept at1 to 2 times the partial pressure of the carbon feedstock. A vacuum pump15 may be provided as shown. It may be desirable to recycle thefeedstock mixture to the growth chamber. As the fiber grows it can bewithdrawn from the growth chamber 16 by a suitable transport mechanismsuch as drive roll 17 and idler roll 18. The growth chamber 16 is indirect communication with a vacuum feed lock zone 19.

[0170] The pressure in the growth chamber can be brought up toatmospheric, if necessary, in the vacuum feed lock by using a series ofchambers 20. Each of these chambers is separated by a loose TEFLONO-ring seal 21 surrounding the moving fiber. Pumps 22 effect thedifferential pressure equalization. A take-up roll 23 continuouslycollects the room temperature carbon fiber cable. Product output of thisprocess can be in the range of 10⁻³ to 10¹ feet per minute or more. Bythis process, it is possible to produce tons per day of continuouscarbon fiber made up of SWNT molecules.

[0171] Growth of the fiber can be terminated at any stage (either tofacilitate manufacture of a fiber of a particular length or when toomany defects occur). To restart growth, the end may be cleaned (i.e.,reopened) by oxidative etching (chemically or electrochemically). Thecatalyst particles can then be reformed on the open tube ends, andgrowth continued.

[0172] The molecular array (template) may be removed from the fiberbefore or after growth by macroscopic physical separation means, forexample by cutting the fiber with scissors to the desired length. Anysection from the fiber may be used as the template to initiateproduction of similar fibers.

[0173] The continuous carbon fiber of the present invention can also begrown from more than one separately prepared molecular array ortemplate. The multiple arrays can be the same or different with respectto the SWNT type or geometric arrangement in the array. Large cable-likestructures with enhanced tensile properties can be grown from a numberof smaller separate arrays as shown in FIG. 8. In addition to themasking and coating techniques described above, it is possible toprepare a composite structure, for example, by surrounding a centralcore array of metallic SWNTs with a series of smaller circularnon-metallic SWNT arrays arranged in a ring around the core array asshown in FIG. 9.

[0174] Not all the structures contemplated by this invention need beround or even symmetrical in two-dimensional cross section. It is evenpossible to align multiple molecular array seed templates in a manner asto induce nonparallel growth of SWNTs in some portions of the compositefiber, thus producing a twisted, helical rope, for example. It is alsopossible to catalytically grow macroscopic carbon fiber in the presenceof an electric field to aid in alignment of the SWNTs in the fibers, asdescribed above in connection with the formation of template arrays.

Random Growth of Carbon Fibers from SWNTs

[0175] While the continuous growth of ordered bundles of SWNTs describedabove is desirable for many applications, it is also possible to produceuseful compositions comprising a randomly oriented mass of SWNTs, whichcan include individual tubes, ropes and/or cables. The random growthprocess has the ability to produce large quantities, i.e., tons per day,of SWNT material.

[0176] In general the random growth method comprises providing aplurality of SWNT seed molecules that are supplied with a suitabletransition metal catalyst as described above, and subjecting the seedmolecules to SWNT growth conditions that result in elongation of theseed molecule by several orders of magnitude, e.g., 10² to 10¹⁰ or moretimes its original length.

[0177] The seed SWNT molecules can be produced as described above,preferably in relatively short lengths, e.g., by cutting a continuousfiber or purified bucky paper. In a preferred embodiment, the seedmolecules can be obtained after one initial run from the SWNT feltproduced by this random growth process (e.g., by cutting). The lengthsdo not need to be uniform and generally can range from about 5 nm to 10μm in length.

[0178] These SWNT seed molecules may be formed on macroscale ornanoscale supports that do not participate in the growth reaction. Inanother embodiment, SWNTs or SWNT structures can be employed as thesupport material/seed. For example, the self assembling techniquesdescribed below can be used to form a three-dimensional SWNTnanostructure. Nanoscale powders produced by these technique have theadvantage that the support material can participate in the random growthprocess.

[0179] The supported or unsupported SWNT seed materials can be combinedwith a suitable growth catalyst as described above, by opening SWNTmolecule ends and depositing a metal atom cluster. Alternatively, thegrowth catalyst can be provided to the open end or ends of the seedmolecules by evaporating a suspension of the seeds in a suitable liquidcontaining a soluble or suspended catalyst precursor. For example, whenthe liquid is water, soluble metal salts such as Fe (NO₃)₃, Ni (NO₃)₂ orCO (NO₃)₂ and the like may be employed as catalyst precursors. In orderto insure that the catalyst material is properly positioned on the openend(s) of the SWNT seed molecules, it may be necessary in somecircumstances to derivitize the SWNT ends with a moiety that binds thecatalyst nanoparticle or more preferably a ligand-stabilized catalystnanoparticle.

[0180] In the first step of the random growth process the suspension ofseed particles containing attached catalysts or associated withdissolved catalyst precursors is injected into an evaporation zone wherethe mixture contacts a sweep gas flow and is heated to a temperature inthe range of 250-500° C. to flash evaporate the liquid and provide anentrained reactive nanoparticle (i.e., seed/catalyst). Optionally thisentrained particle stream is subjected to a reduction step to furtheractivate the catalyst (e.g., heating from 300-500° C. in H₂) Acarbonaceous feedstock gas, of the type employed in the continuousgrowth method described above, is then introduced into the sweepgas/active nanoparticle stream and the mixture is carried by the sweepgas into and through a growth zone.

[0181] The reaction conditions for the growth zone are as describedabove, i.e., 500-1000° C. and a total pressure of about one atmosphere.The partial pressure of the feedstock gas (e.g., ethylene, CO) can be inthe range of about 1 to 100 Torr. The reaction is preferably carried outin a tubular reactor through which a sweep gas (e.g., argon) flows.

[0182] The growth zone may be maintained at the appropriate growthtemperature by 1) preheating the feedstock gas, 2) preheating the sweepgas, 3) externally heating the growth zone, 4) applying localizedheating in the growth zone, e.g. by laser or induction coil, or anycombination of the foregoing.

[0183] Downstream recovery of the product produced by this process canbe effected by known means such as filtration, centrifugation and thelike. Purification may be accomplished as described above. Felts made bythis random growth process can be used to make composites, e g, withpolymers, epoxies, metals, carbon (i.e., carbon/carbon materials) andhigh −T_(c) superconductors for flux pinning.

Macroscopic Carbon Fiber

[0184] The macroscopic carbon fiber produced as described herein is madeup of an aggregate of large number of single-wall nanotubes preferablyin generally parallel orientation. While individual nanotubes maydeviate from parallel orientation relative to any other individualnanotube, particularly for very short distances, over macroscopicdistances the average orientation of all of the nanotubes preferablywill be generally parallel to that of all other nanotubes in theassembly (macroscopic distances as described herein are generallyconsidered to be greater than 1 micron). In one preferred form, theSWNTs will be arranged in a regular triangular lattice, i.e., in aclosest packing relationship.

[0185] The carbon fiber of this invention is made up of individualtubular molecules and may be in whole or in part either crystalline oramorphous in structure. The degree of order in the fiber will dependboth on the geometric relationship of the tubes in the molecular arrayand the growth and annealing conditions. The fiber may be subjected toorientation or other post-formation treatments before or aftercollection. The fiber produced by this process may, for example, befurther spun or braided into larger yarns or cables. It is alsocontemplated that as produced fiber will be large enough in diameter formany applications.

[0186] Generally, the macroscopic carbon fiber produced according tothis invention consists of a sufficient number of substantially parallelsingle-wall nanotubes that it is large enough in diameter to bepractically handled as an individual fiber and/or processed into largercontinuous products. The macroscopic nature of the assembly of nanotubesis also important for end uses such as transmission of electric currentover these nanotube cables. A macroscopic carbon fiber according to thisinvention preferably will contain at least 10⁶ single-wall carbonnanotubes, and more preferably at least 10⁹ single-wall carbonnanotubes. The number of assembled nanotubes is vastly larger than thenumber (<10³) that spontaneously align during the formation ofsingle-wall nanotube ropes in the condensing carbon vapor of a carbonarc or laser vaporization apparatus. For many applications the preferreddiameter of the macroscopic carbon fiber of this invention will be inthe range of from about 1 to about 10 microns. Some applications, e.g.,power transmission cables, may require fiber diameters of up to a fewcentimeters. It is also possible to include dopants, e.g., metals,halogens, FeCl₃ and the like, physically entrapped between the tubes ofthe fiber.

[0187] The macroscopic carbon fiber of this invention will generally beat least 1 millimeter in length, with the exact length depending uponthe particular application for which the fiber is used. For example,where the fiber is designed to substitute for conventional graphitecarbon fiber for reinforcing, the length of the fiber according to thisinvention will be similar to the length of the convention carbon fibers.Where the macroscopic carbon fiber according to this invention is usedfor electrical conductance, the length of the fiber preferablycorresponds to the distance over which electrical conductance isdesired. Typically such distances may be from 1-100 microns or up to1-10 millimeters or greater. Where conductance over macroscopicdistances is desired, it is preferred that the macroscopic carbon fiberaccording to this invention have a length on the order of meters orgreater.

[0188] One reason the continuous carbon fiber of the present inventionhas such improved physical properties is its structure as a high orderlaminate—as many as 10⁹ or more individual tubular molecules arelaminated together. This structure provides much higher strength inbending, significantly higher resistance to failure by chemicalcorrosion, better wear, more elasticity and a completely differenttensile failure mechanism from similar monolithic materials. Thesingle-wall carbon nanotube fiber of this invention provides extremelyhigh tensile strength at low weight (˜100 times stronger than steelwhile having only one sixth the weight). This fiber has an electricalconductivity similar to copper. In addition the thermal conductivityalong the fiber is approximately that of diamond. The carbon fiber ofthis invention also has high chemical resistance (better than spheroidalfullerenes such as C⁶⁰-C⁷⁰). In general the substantially defect-freecontinuous carbon fiber of this invention will exhibit improvedproperties over conventional carbon fibers because of its near perfectmulti-hexagonal structure that extends over macroscopic distances.

[0189] In a particular embodiment, macroscopic carbon fiber according tothis invention is grown from a molecular array comprising a SAM having aregion substantially comprising single-wall nanotubes in armchairorientation, the region having a diameter of at least one micron andpreferably at least 100 microns. By use of masks on the surface uponwhich the monolayer is assembled, the area containing single-wallednanotubes in armchair structure is completely surrounded on all sides bya concentric region of tubes having a chiral or zig-zag structure.Elongation from this template will produce a conducting core surroundedby a semiconducting or insulating sheath, each layer made up of singlemolecules of essentially infinite length. In a similar manner, aco-axial transmission cable with several layers can be produced.

[0190] Applications of these carbon fibers include all those currentlyavailable for graphite fibers and high strength fibers such as membranesfor batteries and fuel cells; chemical filters; catalysts supports;hydrogen storage (both as an absorbent material and for use infabricating high pressure vessels); lithium ion batteries; and capacitormembranes. These fibers can also be used in electromechanical devicessuch as nanostrain gauges (sensitive to either nanotube bend or twist).Fibers of this invention can be used as product or spun into threads orformed into yarns or to fibers using known textile techniques.

[0191] The carbon fiber technology of this invention also facilitates aclass of novel composites employing the hexaboronitride lattice. Thismaterial forms graphene-like sheets with the hexagons made of B and Natoms (e.g., B₃ N₂ or C₂ BN₃). It is possible to provide an outercoating to a growing carbon fiber by supplying a BN precursor (e.g.,tri-chloroborazine, a mixture of NH₃ and BCl₃ or diborane) to the fiberwhich serves as a mandrel for the deposition of BN sheets. This outer BNlayer can provide enhanced insulating properties to the metallic carbonfiber of the present invention. Outer layers of pyrolytic carbonpolymers or polymer blends may also be employed to impart. By changingthe feedstock in the above described process of this invention from ahydrocarbon to a BN precursor and back again it is possible to grow afiber made up of individual tubes that alternate between regions of allcarbon lattice and regions of BN lattice. In another embodiment of thisinvention, an all BN fiber can be grown by starting with a SWNT templatearray topped with a suitable catalyst and fed BN precursors. Thesegraphene and BN systems can be mixed because of the very close match ofsize to the two hexagonal units of structure. In addition, they exhibitenhanced properties due to the close match of coefficients of thermalexpansion and tensile properties. BN fibers can be used in composites asreinforcing and strengthening agents and many of the other usesdescribed above for carbon fibers.

Device Technology Enabled by Products of this Invention

[0192] The unique properties of the tubular carbon molecules, moleculararrays and macroscopic carbon fibers of the present invention provideexciting new device fabrication opportunities.

[0193] 1. Power Transmission Cable

[0194] Current power transmission-line designs generally employ aluminumconductors, often with steel strand cores for strength (i.e., theso-called ASCR conductor). The conductors have larger losses than copperconductors and generally are not shielded leading to corona dischargeproblems. The continuous carbon fibers made form large (>10⁶)aggregations of SWNTs can be used to fabricate power transmission cablesof unique designs and properties. One such design is shown in FIG. 10.This design is essentially a shielded coaxial cable capable of EHV(extra high voltage) power transmission, (i.e., >500 KV and preferablyover 10⁶ V) and having heretofore unattainable strength-to-weightproperties and little or no corona discharge problems.

[0195] The illustrated design which exemplifies the use of theSWNT-based carbon fiber conductors produced as described above (e.g.,from n,n metallic SWNTs), consists of a central conductor 30 and acoaxial outer conductor 31, separated by an insulating layer 32. Thecentral conductor carries the power transmission which the outer layerconductor is biased to ground. The central conductor can be a solidmetallic carbon fiber. Alternatively, the central conductor can comprisea bundle of metallic carbon fiber strands which may be aggregatedhelically as is common in ACSR conductors.

[0196] The inner conductor can also comprise an annular tube surroundingan open core space in which the tube is a woven or braided fabric madefrom metallic carbon fibers as described above. The insulating layer canbe any light weight insulating material. Among the preferred embodimentsare strands or woven layers of BN fibers made as described above and theuse of an annular air space (formed using insulating spacers).

[0197] The outer conductor layer is also preferably made from hexicallywound strands of metallic carbon fiber as described above. This groundedlayer essentially eliminates corona discharge problems or the need totake conventional steps to reduce these emissions.

[0198] The resulting coaxial structure possesses extremely highstrength-to-weight properties and can be used to transmit greater thanconventional power levels over greater distances with lower losses.

[0199] One of the above described power cable assemblies can be used toreplace each of the conductors used for separate phases in theconventional power transmission system. It is also possible byfabricating a multilayer annular cable with alternating metallic carbonfiber conductors and insulating layers to provide a single powertransmission-cable carrying three or more phases, thus greatlysimplifyig the installation and maintenance of power lines.

[0200] 2. Solar Cell

[0201] A Grätzel cell of the type described in U.S. Pat. No. 5,084,365(incorporated herein by reference in its entirety) can be fabricatedwith the nanocrystalline TiO₂ replaced by a monolayer molecular array ofshort carbon nanotube molecules as described above. The photoactive dyeneed not be employed since the light energy striking the tubes will beconverted into an oscillating electronic current which travels along thetube length. The ability to provide a large charge separation (thelength of the tubes in the array) creates a highly efficient cell. It isalso contemplated by the present invention to use a photoactive dye(such as cis-[bisthiacyanato bis (4,4′-dicarboxy-2-2′-bipyridine Ru(II))] attached to the end of each nanotube in the array to furtherenhance the efficiency of the cell. In another embodiment of the presentinvention, the TiO₂ nanostructure described by Grätzel can serve as anunderlying support for assembling an array of SWNT molecules. In thisembodiment, SWNTs are attached directly to the TiO₂ (by absorptiveforces) or first derivatized to provide a linking moiety and then boundto the TiO₂ surface. This structure can be used with or without aphotoactive dye as described above.

[0202] 3. Memory Device

[0203] The endohedrally loaded tubular carbon molecule described abovecan be used to form the bit structure in a nanoscale bistablenon-volatile memory device. In one form, this bit structure comprises aclosed tubular carbon molecule with an enclosed molecular entity thatcan be caused to move back and forth in the tube under the influences ofexternal control. It is also possible to fill a short nanotube moleculewith magnetic nanoparticles (e.g., Ni/Co) to form a nanobit useful inmagnetic memory devices.

[0204] One preferred form of a bit structure is shown in FIG. 11. Thetubular carbon molecule 40 in this bit should be one that exhibits agood fit mechanically with the movable internal moiety 41, i.e., not toosmall to impede its motion. The movable internal moiety should be chosen(1) to facilitate the read/write system employed with the bit and (2) tocompliment the electronic structure of the tube.

[0205] One preferred arrangement of such a nanobit employs a shortclosed tubular carbon molecule (e.g., about 10-50 nm long) made from a(10,10) SWNT by the above-described process, and containing encapsulatedtherein a C₆₀ or C₇₀ spheroidal fullerene molecule. Optionally the C₆₀or C₇₀ molecule (bucky ball) can be endohedrally or exohedrally doped.The C₆₀ bucky ball is almost a perfect fit in a (10,10) tube. Moreimportantly, the electronic environment inside the tube is highlycompatible with that of the bucky bail, particularly at each end, sincehere the inner curvature of the (10, 10) tube at the end cap matches theouter curvature of the bucky ball. This configuration results in optimumvan der Waals interaction. As shown in FIG. 12, the energy thresholdrequired to get one bucky ball out of the end cap (where it is in themost electronically stable configuration) serves to render the bitbistable.

[0206] One preferred read/writ structure for use with the memory bitdescribed above is shown in FIG. 11. Writing to the bit is accomplishedby applying a polarized voltage pulse through a nanocircuit element 42(preferably a SWNT molecule). A positive pulse will pull the bucky balland a negative pulse will push the bucky ball. The bistable nature ofthe bit will result in the bucky ball staying in this end of the tubewhen the pulse is removed since that is where the energy is lowest. Toread the bit, another nanocircuit element 43 (again preferable, a SWNTmolecule) is biased with a V_(READ). If the bucky ball is present in thedetection end, it supplies the necessary energy levels for current toresonantly tunnel across the junction to the ground voltage 44 (in afashion analogous to a resonant tunneling diode) resulting in a firststable state being read. If the bucky ball is not present in thedetection end, the energy levels are shifted out of resonance and thecurrent does not tunnel across the junction and a second stable state isread. Other forms of read/write structure (e.g., microactuators) can beemployed as will be recognized by one skilled in the art.

[0207] A memory device can be constructed using either a two- orthree-dimensional array of the elements shown in FIG. 12. Because theelements of the memory array are so small (e.g., ˜5 nm×25 nm), extremelyhigh bit densities can be achieved, i.e., >1.0 terabit/cm² (i.e., a bitseparation of 7.5 nm). Because the bucky ball only has to move a fewnanometers and its mass is so small, the write time of the describeddevice is on the order of 10−10 seconds.

[0208] 4. Lithium Ion Battery

[0209] The present invention also relates to a lithium ion secondarybattery in which the anode material includes a molecular array of SWNTsmade as described above (e.g., by SAM techniques). The anode materialcan comprise a large number (e.g., >10³) short nanotube molecules boundto a substrate. Alternatively, the end of a macroscopic carbon fiber asdescribed above can serve as the microporous anode surface.

[0210] The tubular carbon molecules in this array may be open or closed.In either case, each tubular carbon molecule provides a structurallystable microporosity for the intercalation of lithium ions, i.e., intothe open tubes or into triangular pores of an end cap. The resultingfullerene intercalation compound (FIC) can be used, for example, with anaprotic organic electrolyte containing lithium ions and a LiCoO₂ cathodeto form an improved lithium ion secondary battery of the type describedin Nishi, “The Development of Lithium Ion Secondary Batteries,” 1996IEEE symposium on VLSI Circuits and shown in FIG. 13. In this figure,the anode 50 comprises a large number of SWNTs 51 in an orderedmolecular array. Cathode 52, electrolyte 53, lithium ions 54 andelectrons 55 make up the remaining elements of the cell.

[0211] The use of the molecular array FICs of this invention provides alithium-storing medium that has a high charge capacity (i.e., >600 mAh/g) which is stable during charging and possesses excellent cylabilityand that results in an improved safe rechargeable battery.

[0212] The anode is characterized by high current, high capacity, lowresistance, highly reversible and is nano-engineered from carbon withmolecular perfection. The anode is constructed as a membrane of metallicfullerene nanotubes arrayed as a bed-of-nails, the lithium atoms beingstored in the spaces either between the adjacent tubes or down thehollow pore within each tube. Chemical derivatization of the open endsof the tubes will then be optimized to produce the best possibleinterface with the electrolyte. The derivative is preferably an organicmoiety which provides a stable interface where the redox reaction canoccur. In general, the organic moiety should be similar in structure tothe electrolyte. One preferred derivitizing agent is polyethylene oxideand, in particular, polyethylene oxide oligomers.

[0213] The electrochemistry of the nano-engineered nanotube membranesare used for electrode applications. Important aspects are to derivatizetheir ends and sides in such a way as to provide an optimal interfacefor a lithium-ion battery electrolyte. This will result in a batteryelectrode that is highly accessible to the lithium ions, thereforecapable of delivering high power density, and equally important,overcomes the ubiquitous SEI (solid-electrolyte interface) problem thatsignificantly reduces electrode capacity and reversibility.

[0214] Li⁺ is the ion choice for rechargeable batteries. Bested only bythe proton as a lightweight counter-ion, Li profits from theavailability of a wide class of solid and liquid electrolytes as a largechoice of cathode materials, primarily metal oxides with 3D networks ofintercalation sites in which the Li⁺ resides in the discharged state.The first rechargeable Li batteries used metallic Li as an anode, butseveral drawbacks existed:

[0215] loss of Li due to dendrite growth during recharging;

[0216] safety problems associated with the reactivity of Li metal in thepresence of organic solvents; and

[0217] the potential for anode-cathode shorts through the separator dueto the aforementioned Li dendrites.

[0218] A solution to the safety problems was found by replacing Li metalby a Li-carbon intercalation anode, giving birth to the “rocking chair”battery in which the Li is never reduced to Li⁰ and Li⁺ shuttles betweenintercalation sites in the carbon anode and metal cathode as the batteryis charged and discharged respectively. Graphite was used in the firstgeneration Li-ion batteries, largely because the solid state chemistryof Li-graphite was well understood. Happily, the potential of Li⁺ ingraphite is within a few tens of MV of the potential of Li⁰, so the useof graphite in place of Li metal imposes a small weight and volumepenalty but no significant penalty in cell voltage.

[0219] But the use of graphite brought its own problems to thetechnology:

[0220] the best electrolytes (e.g., LiClO₄ dissolved in propylenecarbonate) which have good Li⁺ conductivity at ambient T alsoco-intercalate by solvating the Li⁺,leaving to exfoliation of thegraphite, dimensional instabilities and premature failure, and

[0221] the diffusivity of Li⁺ in graphite is rather low at ambient T,controlled by the large barrier for jump diffusion (commensuratelattice) between adjacent hexagonal interstitial sites in the graphitelattice.

[0222] The first problem was overcome by the development of newelectrolytes which did not co-intercalate, e.g., LiPF₆ in a mixture ofdimethyl carbonate and ethylene carbonate, which however had adetrimental effect on the electrolyte contribution to ion transportlinetics. The second prolem required the use of finely divided graphite(powder, chopped fibers, foams) which in turn increased the surface areasubstantially, leading inexorably to yet a new set of problems, namelycapacity fade due to the formation of surface film (SEI:“solid-electrolyte interphase”) during the first anode intercalationhalf-cycle. This in turn required assembling the battery with extraLi-containing cathode material to provide for the Li consumed by SEIformation, thus reducing the capacity. Not much is known about the SEI,but it is widely agreed that the carbonates (from electrolytedecomposition) are an important constituent. A widely accepted criterionin industry is that capacity loss due to SEI formation should not exceed10% of the available Li.

[0223] Subsequent research explored the use of other forms of(nanocrystalline) carbon: carbon black, pyrolyzed coal and petroleumpitches and polymers, pyrolyzed natural products (sugars, nutshells,etc.), “alloys” of carbon with other elements (boron, silicon, oxygen,hydrogen), and entirely new systems such as tin oxides. Some of theseexhibit much lager Li capacities than graphite, but the microscopicorigins of this “excess capacity” are largely unknown. In general thecycling behavior of these materials is much worse than graphite, and thehydrogen-containing materials also exhibit large hysteresis in cellpotential vs. Li concentration between charge and discharge half-cycles,a very undesirable property for a battery. Again, the origin of thehysteresis is largely unknown. The main advantage of these materials isthat their inherently finely-divided nature augurs well for fastkinetics, an absolute prerequisite if LIB's are to have an impact inhigh current applications (e.g., electric vehicle).

[0224] The anode of the present invention is entirely nano-fabricatedwith molecular precision. It has a large capacity per unit volume tostore lithium at an electrochemical potential near that of lithiummetal, and is protected from the dendrite growth problems and safetyconcerns that plague pure metal anodes. It has extremely fast kineticsfor charging and discharging, but maintain its architectural andchemical integrity in at all states of charge and discharge. Inaddition, there is a means for custom designing the interface betweenthis anode and the electrolyte such that the Li⁰⇄Li⁺¹ redox chemistry ishighly reversible and very low in effective resistance.

[0225] A design for such an anode is one which consists of an array offullerene nanotubes, attached to a metallic support electrode, such asgold-coated copper, and arranged in a hexagonal lattice much like a bedof nails. As shown in FIG. 14, this structure has the virtue that thestorage area for the reduced state of the lithium, Li⁰, is down deepchannels either between the nanotubes or down the hollow core of thetubes themselves. Accordingly, the redox chemistry of the lithium isconfined primarily to the exposed ends of the nanotubes, and herederivatization of the nanotube ends provides great opportunities toinsure that this redox chemistry is as reversible as possible.

[0226] 5. Three-Dimensional Self-Assembling SWNT Structures

[0227] The self-assembling structures contemplated by this invention arethree-dimensional structures of derivatized SWNT molecules thatspontaneously form when the component molecules are brought together. Inone embodiment the SAM, or two-dimensional monolayer, described abovemay be the starting template for preparing a three dimensionalself-assembling structures. Where the end caps of the component SWNTmolecules have mono-functional derivatives the three-dimensionalstructure will tend to assemble in linear head-to-tail fashion. Byemploying multi-functional derivatives or multiple derivatives atseparate locations it is possible to create both symmetrical and nonsymmetrical structures that are truly three-dimensional.

[0228] Carbon nanotubes in material obtained according to the foregoingmethods may be modified by ionically or covalently bondingfunctionally-specific agents (FSAs) to the nanotube. The FSAs may beattached at any point or set of points on the fullerene molecule. TheFSA enables self-assembly of groups of nanotubes into geometricstructures. The groups may contain tubes of differing lengths and usedifferent FSAs. Self-assembly can also occur as a result of van derwaals attractions between derivitized or underivitized or a combinationof derivitized and underivitized fullerene molecules. The bondselectivity of FSAs allow selected nanotubes of a particular size orkind to assemble together and inhibit the assembling of unselectednanotubes that may also be present. Thus, in one embodiment, the choiceof FSA may be according to tube length. Further, these FSAs can allowthe assembling of two or more carbon nanotubes in a specific orientationwith respect to each other.

[0229] By using FSAs on the carbon nanotubes and/or derivitized carbonnanotubes to control the orientation and sizes of nanotubes which areassembled together, a specific three-dimensional structure can be builtup from the nanotube units. The control provided by the FSAs over thethree-dimensional geometry of the self assembled nanotube structure canallow the synthesis of unique three-dimensional nanotube materialshaving useful mechanical, electrical, chemical and optical properties.The properties are selectively determined by the FSA and the interactionof and among FSAs.

[0230] Properties of the self-assembled structure can also be affectedby chemical or physical alteration of the structure after assembly or bymechanical, chemical, electrical, optical, and/or biological treatmentof the self-assembled fullerene structure. For example, other moleculescan be ionically or covalently attached to the fullerene structure orFSAs could be removed after assembly or the structure could berearranged by, for example, biological or optical treatment. Suchalterations and/or modifications could alter or enable electrical,mechanical, electromagnetic or chemical function of the structure, orthe structure's communication or interaction with other devices andstructures.

[0231] Examples of useful electric properties of such a self-assembledgeometric structure include: operation as an electrical circuit, aspecific conductivity tensor, a specific response to electromagneticradiation, a diode junction, a 3-terminal memory device that providescontrollable flow of current, a capacitor forming a memory element, acapacitor, an inductor, a pass element, or a switch.

[0232] The geometric structure may also have electromagnetic propertiesthat include converting electromagnetic energy to electrical current, anantenna, an array of antennae, an array that produces coherentinterference of electromagnetic waves to disperse those of differentwavelength, an array that selectively modifies the propagation ofelectromagnetic waves, or an element that interacts with optical fiber.The electromagnetic property can be selectively determined by the FSAand the interaction of and among FSAs. For example, the lengths,location, and orientation of the molecules can be determined by FSAs sothat an electromagnetic field in the vicinity of the molecules induceselectrical currents with some known phase relationship within two ormore molecules. The spatial, angular and frequency distribution of theelectromagnetic field determines the response of the currents within themolecules. The currents induced within the molecules bear a phaserelationship determined by the geometry of the array. In addition,application of the FSAs could be used to facilitate interaction betweenindividual tubes or groups of tubes and other entities, whichinteraction provides any form of communication of stress, strain,electrical signals, electrical currents, or electromagnetic interaction.This interaction provides an “interface” between the self-assemblednanostructure and other known useful devices.

[0233] Choice of FSAs can also enable self-assembly of compositionswhose geometry imparts useful chemical or electrochemical propertiesincluding operation as a catalyst for chemical or electrochemicalreactions, sorption of specific chemicals, or resistance to attack byspecific chemicals, energy storage or resistance to corrosion.

[0234] Examples of biological properties of FSA self-assembled geometriccompositions include operation as a catalyst for biochemical reactions;sorption or reaction site specific biological chemicals, agents orstructures; service as a pharmaceutical or therapeutic substance;interaction with living tissue or lack of interaction with livingtissue; or as an agent for enabling any form of growth of biologicalsystems as an agent for interaction with electrical, chemical, physicalor optical functions of any known biological systems.

[0235] FSA assembled geometric structure can also have useful mechanicalproperties which include but are not limited to a high elastic tomodulus weight ratio or a specific elastic stress tensor. Opticalproperties of geometric structures can include a specific opticalabsorption spectrum, a specific optical transmission spectrum, aspecific optical reflection characteristic, or a capability formodifying the polarization of light.

[0236] Self-assembled structures, or fullerene molecules, alone or incooperation with one another (the collective set of alternatives will bereferred to as “molecule/structure”) can be used to create devices withuseful properties. For example, the molecule/structure can be attachedby physical, chemical, electrostatic, or magnetic means to anotherstructure causing a communication of information by physical, chemical,electrical, optical or biological means between the molecule/structureand other structure to which the molecule/structure is attached orbetween entities in the vicinity of the molecule/structure. Examplesinclude, but are not limited to, physical communication via magneticinteraction, chemical communication via action of electrolytes ortransmission of chemical agents through a solution, electricalcommunication via transfer of electronic charge, optical communicationvia interaction with and passage of any form with biological agentsbetween the molecule/structure and another entity with which thoseagents interact.

[0237] 6. SWNT Antenna

[0238] Fullerene nanotubes can be used to replace the more traditionalconductive elements of an antenna. For example, an (n,n) tube inconjunction with other materials can be used to form a Schottky barrierwhich would act as a light harvesting antenna. In one embodiment, a(10,10) tube can be connected via sulfur linkages to gold at one end ofthe tube and lithium at the other end of the tube forming a naturalSchottky barrier. Current is generated through photo conductivity. Asthe (10,10) tube acts like an antenna, it pumps electrons into oneelectrode, but back flow of electrons is prevented by the intrinsicrectifying diode nature of the nanotube/metal contact.

[0239] In forming an antenna, the length of the nanotube can be variedto achieve any desired resultant electrical length. The length of themolecule is chosen so that the current flowing within the moleculeinteracts with an electromagnetic field within the vicinity of themolecule, transferring energy from that electromagnetic field toelectrical current in the molecule to energy in the electromagneticfield. This electrical length can be chosen to maximize the currentinduced in the antenna circuit for any desired frequency range. Or, theelectrical length of an antenna element can be chosen to maximize thevoltage in the antenna circuit for a desired frequency range.Additionally, a compromise between maximum current and maximum voltagecan be designed.

[0240] A Fullerene nanotube antenna can also serve as the load for acircuit. The current to the antenna can be varied to produce desiredelectric and magnetic fields. The length of the nanotube can be variedto provide desired propagation characteristics. Also, the diameter ofthe antenna elements can be varied by combining strands of nanotubes.

[0241] Further, these individual nanotube antenna elements can becombined to form an antenna array. The lengths, location, andorientation of the molecules are chosen so that electrical currentswithin two or more of the molecules act coherently with some known phaserelationship, producing or altering an electromagnetic field in thevicinity of the molecules. This coherent interaction of the currentswithin the molecules acts to define, alter, control, or select thespatial, angular and frequency distributions of the electromagneticfield intensity produced by the action of these currents flowing in themolecules. In another embodiment, the currents induced within themolecules bear a phase relationship determined by the geometry of thearray, and these currents themselves produce a secondary electromagneticfield, which is radiated from the array, having a spatial, angular andfrequency distribution that is determined by the geometry of the arrayand its elements. One method of forming antenna arrays is theself-assembly monolayer techniques discussed above.

[0242] 7. Fullerene Molecular Electronics

[0243] Fullerene molecules can be used to replace traditionalelectrically conducting elements. Thus fullerene molecules orself-assembled fullerene groups can be the basis of electrical circuitsin which the molecule transfers electrical charge between functionalelements of the circuit which alter or control the flow of that chargeor objects in which the flow of electrical current within the objectperforms some useful function such as the redistribution of the electricfield around the object or the electric contact in a switch or aresponse of the object to electromagnetic waves.

[0244] As an example, nanotubes can also be self-assembled to form abridge circuit to provide full wave rectification. This device caninclude four nanotubes, each forming an edge of a square, and fourbuckyballs, one buckyball would be located at each corner of the square.The buckyballs and nanotubes can be derivitized to include functionallyspecific agents. The functionally specific agents form linkagesconnecting the buckyballs to the nanotubes and imparting the requiredgeometry of the bridge.

[0245] A fullerene diode can be constructed through the self-assemblytechniques described above. The diode can be composed of two bucky tubesand a bucky capsule. The bucky capsule can also be derivitized to form azwiterrion. For example, the bucky capsule can include two positivegroups, such as the triethyl amine cation and two negative groups, suchas CO₂- anion. In one embodiment, each end of the bucky capsule isconnected to a (10,10) bucky tube by a disulfide bridge. Thus, sulfurserves as the functionally-specific agent.

[0246] 8. Probes and Manipulators

[0247] The SWNT molecules of the present invention also enable thefabrication of probes and manipulators on a nanoscale. Probe tips forAFM and STW equipment and AFM cantilevers are examples of such devices.Derivatized probes can serve as sensors or sensor arrays that effectselective binding to substrates. Devices such as these can be employedfor rapid molecular-level screening assays for pharmaceuticals and otherbioactive materials. Further, conducting SWNT molecules of the presentinvention may also be employed as an electrochemical probe.

[0248] Similarity probe-like assemblies of SWNT molecules can be usedwith or without derivatives as tools to effect material handling andfabrication of nanoscale devices, e.g., nanoforcepts. In addition, thesemolecular tools can be used to fabricate MEMS (Micro Electro MechanicalSystems) and also can be employed as connecting elements or circuitelements in NANO-MEMS.

[0249] 9. Composite Materials Containing Carbon Nanotubes

[0250] Composite materials, i.e., materials that are composed of two ormore discrete constituents, are known. Typically, composites include amatrix, which serves to enclose the composite and give it its bulk form,and a structural constituent, which determines the internal structure ofthe component. The matrix deforms and distributes an applied stress tothe structural constituent.

[0251] Although composites are generally extremely strong, theirstrength is generally anisotropic, being much less in the directionperpendicular to the plane of the composite material than any paralleldirection. Because of this characteristic, composites that are formed inlayers or in laminate strips are prone to delamination. Delamination mayoccur when at least one layer of the composite separates from theothers, resulting in a void in the bulk of the composite material. Thisvoid is exceedingly difficult to detect, and with repeated applicationsof stress to the composite element, the composite element will failcatastrophically, without warning.

[0252] Carbon nanotubes may serve as structural constituents incomposite materials. As discussed above composite materials aregenerally composed of two or more discrete constituents, usuallyincluding a matrix, which gives the composite its bulk form, and atleast one structural constituent, which determines the internalstructure of the composite. Matrix materials useful in the presentinvention can include any of the known matrix materials presentlyemployed (see e. Mel M. Schwartz, Composite Materials Handbook (2d ed.1992)). Among those known matrix materials are resins (polymers), boththermosetting and thermoplastic, metals, ceramics, and cermets.

[0253] Thermosetting resins useful as matrix materials includephthalic/maelic type polyesters, vinyl esters, epoxies, phenolics,cyanates, bismaleimides, and nadic end-capped polyimides (e.g., PMR-15).Thermoplastic resins include polysulfones, polyamides, polycarbonates,polyphenylene oxides, polysulfides, polyether ether ketones, polyethersulfones, polyamide-imides, polyetherimides, polyimides, polyarylates,and liquid crystalline polyester. In a preferred embodiment, epoxies areused as the matrix material.

[0254] Metals useful as matrix materials include alloys of aluminum suchas aluminum 6061, 2024, and 713 aluminum braze. Ceramics useful asmatrix materials include glass ceramics, such as lithiumaluminosilicate, oxides such as alumina and mullite, nitrides such assilicon nitride, and carbides such as silicon carbide. Cermets useful asmatrix materials include carbide-base cermets (tungsten carbide,chromium carbide, and titanium carbide), refractory cements(tungsten-thoria and barium-carbonate-nickel), chromium-alumina,nickel-magnesia, and iron-zirconium carbide.

[0255] The carbon nanotube structural constituent according to thepresent invention can take any of the forms described herein and knownin the art. Preferably, a fullerene nanotube, i.e., a carbon nanotubewith molecular perfection, is used. Fullerene nanotubes are made of asingle, continuous sheet of hexagonal graphene joined perfectly to forma tube with a hemifullerene cap at either end. It may be either a truesingle-walled fullerene tube itself with hemispherical caps attached, orit may refer to one derived from such a closed tube by cutting, etchingoff the ends, etc. Alternatively, it is a multi-walled fullerenenanotube constructed of some number of single-walled fullerene nanotubesarranged one inside another. Arc-grown multi-walled nanotubes (MWNT),though approaching the fullerene ideal are still not perfect. They havesignificant structural defects of lesions at least every 100 nm or so ormore in their multiple walls. The single-walled carbon nanotubes made bythe laser/oven method, however, appear to be molecularly perfect. Theyare fullerene nanotubes, and fibers made from them are true fullerenefibers.

[0256] The single-wall fullerene nanotubes may be metallic (formed inthe armchair or (n,n) configuration) or any other helicityconfiguration. The nanotubes may be used in the form of short individualtubular molecules cut to any appropriate length. Cut nanotubes have theheretofore unachievable advantage of providing strengthening andreinforcement on a molecular scale. As they approach the micron scale inlength, however, they become very flexible while still retaining therigid tubular properties on a molecular scale.

[0257] Aggregates of individual tubes referred to herein as ropes havingup to about 10³ carbon nanotubes may also be employed. Ropes of carbonnanotubes produced as described above have the advantage of anentangled, loopy physical configuration on a micron scale that resultsin a Velcro-like interaction with each other and matrix material whilestill retaining the rigid tubular bundle structure on a molecular level.

[0258] Macroscopic carbon nanotube fibers (having at least 10⁶individual tubes), in either the continuous or random fiber formsdescribed above, can also be employed to form the composite of thepresent invention. Ropes and fibers may be cut into desired lengths asdescribed herein or used as tangled, loopy felts or the like.

[0259] The present invention also contemplates composites in whichcarbon nanotubes are present in two or more of the foregoing forms,e.g., mixed in the same matrix area or having different nanotube formsin different areas of the matrix. Selection of the carbon nanotube formwill depend on the nature of the composite and its desired finalproperties. The carbon nanotubes are preferably cleaned and purified asdescribed herein before use.

[0260] The nanotubes, ropes, or fibers used in the composites may alsobe derivatized as described above. End cap derivatization of carbonnanotubes can facilitate the bonding of the carbon nanotubes to eachother or to the matrix material. While pure carbon nanotubes generallycontain side walls that are entirely uniform (consisting of an array ofthe hexagonal carbon lattice similar to that of graphite), it ispossible to introduce defects or create bonding sites in the sidewallsto facilitate bonding adhesion to the matrix material. One example wouldbe to incorporate an impurity such as Boron atoms in the side wall. Thewall defect or bonding site thus created may facilitate interaction ofthe nanotube with the matrix material through physical or chemicalforces. It is additionally possible that such defect or bonding site mayfacilitate chemical reactions between the tube itself and the matrixmaterial in a way that affects the properties of the composite materialformed. As described above, the carbon nanotube material may also have apart of its lattice replaced with boron nitride.

[0261] Other fibrous structural constituents, both organic andinorganic, may also be used in conjunction with the carbon nanotubematerials of this invention. Examples of organic constituents that maybe used include cellulose. Examples of inorganic constituents includecarbon, glass (D, E, and S-type), graphite, silicon oxide, carbon steel,aluminum oxide, beryllium, beryllium oxide, boron, boron carbide, boronnitride, chromium, copper, iron, nickel, silicon carbide, siliconnitride, FP alumina yarn manufactured by DuPont, Nextelalumina-boria-silica and zirconia-silica manufactured by 3M, Saffil HTzircona and alumina manufacture by ICI, quartz, molybdenum, René 41,stainless steel, titanium boride, tungsten, and zirconium oxide.

[0262] Fabrication of the composite of the present invention can employany of the well-known techniques for combining the matrix material withthe structural constituent. Carbon nanotubes, as individual tubularmolecules or as ropes, can be dispersed in a liquid carrier, e.g., wateror organic solvents, to facilitate incorporation into a matrix material.Macroscopic carbon nanotube fibers can be handled in the conventionalmanner employed in the current processes using carbon or graphitefibers.

[0263] The carbon nanotube structural constituent may be uniformly mixedwith a matrix material precursor (polymer solution, pre-fired ceramicparticles or the like) and then converted to a composite by conventionaltechniques. Structural layers or components (e.g., felts or bucky paper)can also be preformed from the carbon nanotube materials and impregnatedwith a prepolymer solution to form the composite.

[0264] The carbon nanotube structural constituents may also be used toimprove the properties of conventional composite materials. One suchexample involves composites built-up of fibrous laminates impregnatedand bonded with a polymer matrix material. Graphite fiber fabric layersbonded with an epoxy system is a well-known example of such a composite.By using carbon nanotube ropes or fibers that exhibit a 3-D loopystructure added only at the epoxy/graphite interfaces, resistance todelamination of the resulting laminar composite can be substantiallyincreased. The carbon nanotube material can be dispersed in the epoxysystem before impregnation (or premixed into one of the reactivecomponents thereof). The carbon nanotube material can also be dispersedin a liquid carrier and sprayed or otherwise applied to the laminate aseach graphite fabric layer is added.

[0265] A single-walled fullerene nanotube such as the (10,10) tube isunique as a component in a composite. From one perspective, it is simplya new molecular polymer, like polypropylene, Nylon, Kevlar, or DNA. Itis about the diameter of the DNA double-helix, but vastly stiffer inbending and stronger in tension. Long chain polymers are characterizedby their persistence length (the distance one has to travel along thelength before there is a substantial change in the chain direction underconditions of normal Brownian motion). For polypropylene, this distanceis only about 1 nm, and for the DNA double-helix it is about 50 nm. Butfor a single (10,10) fullerene nanotube, it is greater than 1000 nm. Soon the persistence length scale of normal polymer molecules such asthose that would constitute the continuous phase of a compositematerial, fullerene nanotubes are effectively rigid pipes.

[0266] Yet on the length scale of a micron or so, a single (10,10)fullerene nanotube is a highly flexible tube, easily becoming involvedwith other nanotubes in tangles with many loops. These tangles and loopsprovide two new opportunities in the internal mechanics of composites:(1) the continuous phase can interpenetrate through these loops, ring inthe nanotubes being intimately “tied” to this phase on a sub-micronlength scale, and (2) with processing by flow and shear of the compositemixture before it sets up, the loops can become entangled in one anotherand pulled taught. As a result, composites made of fullerene tangleshave extra toughness, strength, and resistance to delamination failure.

[0267] Fullerenes like C₆₀ or C₇₀ are known to be effectively spongesfor free radicals. Similarly, fullerene nanotubes such as the (10,10)tube will chemisorb free radicals like methyl, phenyl, methoxy, phenoxy,hydroxy, etc., to their sides. As with the smaller fullerenes, thesechemisorbed species do not substantially weaken the cage network(dissociation at high temperatures simply desorbes the surface species,maintaining the fullerene structure intact). Accordingly, in a compositecontaining fullerene nanotubes, one can achieve a covalent coupling tothe continuous polymer phase simply by attaching pendant groups on thepolymer which produces a free radical upon heating or photolysis withultraviolet light. The azo- linkage, as found inazo-bis-isobutylnitrile, for example, is quite effective as aphoto-activated free radical source.

[0268] The unique properties of the carbon fiber produced by the presentinvention also permit new types of composite reinforcement. It ispossible, for example, to produce a composite fiber/polymer withanisotropic properties. This can, for example, be accomplished bydispersing a number of metallic carbon nanotube fibers (e.g., from (n,n)SWNTs) in a prepolymer solution (e.g., a poly methymethacrylate) andusing an external electric field to align the fibers, followed bypolymerization. Electrically conductive components can also be formedusing the metallic forms of carbon nanotubes.

[0269] Applications of these carbon nanotubes containing compositesinclude, but are not limited to, all those currently available forgraphite fibers and high strength fibers such as Kevlar, including:structural support and body panels and for vehicles, includingautomobiles, trucks, and trains; tires; aircraft components, includingairframes, stabilizers, wing skins, rudders, flaps, helicopter rotorblades, rudders, elevators, ailerons, spoilers, access doors, enginepods, and fuselage sections; spacecraft, including rockets, space ships,and satellites; rocket nozzles; marine applications, including hullstructures for boats, hovercrafts, hydrofoils, sonar domes, antennas,floats, buoys, masts, spars, deckhouses, fairings, and tanks; sportinggoods, including golf carts, golf club shafts, surf boards, hang-gliderframes, javelins, hockey sticks, sailplanes, sailboards, ski poles,playground equipment, fishing rods, snow and water skis, bows, arrows,racquets, pole-vaulting poles, skateboards, bats, helmets, bicycleframes, canoes, catamarans, oars, paddles, and other items;mass-produced modular homes; mobile homes; windmills; audio speakers;furniture, including chairs, lamps, tables, and other modern furnituredesigns; soundboards for string instruments; lightweight armoredproducts for personnel, vehicle, and equipment protection; appliances,including refrigerators, vacuum cleaners, and air conditioners; tools,including hammer handles, ladders, and the like; biocompatible implants;artificial bones; prostheses; electrical circuit boards; and pipes ofall kinds.

EXAMPLES

[0270] In order to facilitate a more complete understanding of theinvention, a number of Examples are provided below. However, the scopeof the invention is not limited to specific embodiments disclosed inthese Examples, which are for purposes of illustration only.

Example 1 Oven Laser-Vaporization

[0271] The oven laser-vaporization apparatus described in FIG. 1 andalso described by Haufler et al., “Carbon Arc Generation of C₆₀ ,” Mat.Res. Soc. Symp. Proc., Vol. 206, p. 627 (1991) and by U.S. Pat. No.5,300,203 was utilized. An Nd:YAG laser was used to produce a scanninglaser beam controlled by a motordriven total reflector that was focusedto a 6 to 7 mm diameter spot onto a metalgraphite composite targetmounted in a quartz tube. The laser beam scans across the target'ssurface under computer control to maintain a smooth, uniform face on thetarget. The laser was set to deliver a 0.532 micron wavelength pulsedbeam at 300 milliJoules per pulse. The pulse rate was 10 hertz and thepulse duration was 10 nanoseconds (ns).

[0272] The target was supported by graphite poles in a 1-inch quartztube initially evacuated to 10 m Torr. and then filled with 500 Torr.argon flowing at 50 standard cubic centimeters per second (scm). Giventhe diameter of the quartz tube, this volumetric flow results in alinear flow velocity through the quartz tube in the range of 0.5 to 10cm/sec. The quartz tube was mounted in a high-temperature furnace with amaximum temperature setting of 1200° C. The high-temperature furnaceused was a Lindberg furnace 12 inches long and was maintained atapproximately 1000° to 1200° C. for the several experiments inExample 1. The laser vaporized material from the target and thatvaporized material was swept by the flowing argon gas from the area ofthe target where it was vaporized and subsequently deposited onto awater-cooled collector, made from copper, that was positioned downstreamjust outside the furnace.

[0273] Targets were uniformly mixed composite rods made by the followingthree-step procedure: (i) the paste produced from mixing high-puritymetals or metal oxides at the ratios given below with graphite powdersupplied by Carbone of America and carbon cement supplied by Dylon atroom temperature was placed in a 0.5 inch diameter cylindrical mold,(ii) the mold containing the paste was placed in a hydraulic pressequipped with heating plates, supplied by Carvey, and baked at 130° C.for 4 to 5 hours under constant pressure, and (iii) the baked rod(formed from the cylindrical mold) was then cured at 810° C. for 8 hoursunder an atmosphere of flowing argon. For each test, fresh targets wereheated at 1200° C. under flowing argon for varying lengths of time,typically 12 hours, and subsequent runs with the same targets proceededafter 2 additional hours heating at 1200° C.

[0274] The following metal concentrations were used in this example.cobalt (1.0 atom percent), copper (0.6 atom percent), niobium (0.6 atompercent), nickel (0.6 atom percent), platinum (0.2 atom percent), amixture of cobalt and nickel (0.6 atom percent/0.6 atom percentrespectively), a mixture of cobalt and platinum (0.6 atom percent/0.2atom percent respectively), a mixture of cobalt and copper (0.6 atompercent/0.5 atom percent respectively), and a mixture of nickel andplatinum (0.6 atom percent/0.2 atom percent respectively). The remainderof the mixture was primarily graphite along with small amounts of carboncement. Each target was vaporized with a laser beam and the sootscollected from the water cooled collector were then collected separatelyand processed by sonicating the soot for 1 hour in a solution ofmethanol at room temperature and pressure (other useful solvents includeacetone, 1,2-dicholoroethane, 1-bromo, 1,2-dichloroethane, andN,N-dimethylformamide). With one exception, the products collectedproduced a homogeneous suspension after 30 to 60 minutes of sonicationin methanol. One sample vaporized from a mixture of cobalt, nickel andgraphite was a rubbery deposit having a small portion that did not fullydisperse even after 2 hours of sonication in methanol. The soots werethen examined using a transmission electron microscope with a beamenergy of 100 keV (Model JEOL 2010).

[0275] Rods (0.5 inch diameter) having the Group VIII transition metalor mixture of two VIII transition metals described above were evaluatedin the experimental apparatus to determine the yield and quality ofsingle-wall carbon nanotubes produced. No multi-wall carbon nanotubeswere observed in the reaction products. Yields always increased withincreasing oven temperature up to the limit of the oven used (1200° C.).At 1200° C. oven temperature, of the single metals utilized in theexample, nickel produced the greatest yield of single-wall carbonnanotubes followed by cobalt. Platinum yielded a small number ofsingle-wall carbon nanotubes and no single-wall carbon nanotubes wereobserved when carbon was combined only with copper or only with niobium.With respect to the mixtures of two Group VIII transition metalcatalysts with graphite, the cobalt/nickel mixture and thecobalt/platinum mixtures were both approximately equivalent and bothwere the best overall catalysts in terms of producing yields ofsingle-wall carbon nanotubes. The yield of single-wall carbon nanotubesfor both of these two metal mires were 10 to 100 times the yieldobserved when only one Group VIII transition metal was used. The mixtureof nickel and platinum with graphite also had a higher yield ofsingle-wall carbon nanotubes than a single metal alone. Thecobalt/copper mixture with graphite produced a small quantity ofsingle-wall carbon nanotubes.

[0276] The cobalt/nickel mixture with graphite and the cobalt/platinummixture with graphite both produced deposits on the water cooledcollector that resembled a sheet of rubbery material. The deposits wereremoved intact. The cobalt/platinum mixture produced single-wall carbonnanotubes in a yield estimated at 15 weight percent of all of the carbonvaporized from the target. The cobalt/nickel mixture producedsingle-wall carbon nanotubes at yields of over 50 wt % of the amount ofcarbon vaporized.

[0277] The images shown in FIGS. 15A through 15E are transmissionelectron micrographs of single-wall carbon nanotubes produced byvaporizing a target comprising graphite and a mixture of cobalt andnickel (0.6 atom percent/0.6 atom percent respectively) at an oventemperature of 1200° C. FIG. 15A shows a medium-magnification view(where the scale bar represents 100 mm) showing that almost everywhere,bundles of single-wall carbon nanotubes are tangled together with othersingle-wall carbon nanotubes. FIG. 15B is a high-magnification image ofone bundle of multiple single-wall carbon nanotubes that are all roughlyparallel to each other. The single-wall carbon nanotubes all have adiameter of about 1 nm, with similar spacing between adjacentsingle-wall carbon nanotubes. The single-wall carbon nanotubes adhere toone another by van der Waals forces.

[0278]FIG. 15C shows several overlapping bundles of single-wall carbonnanotubes, again showing the generally parallel nature of eachsingle-wall nanotube with other single-wall carbon nanotubes in the samebundle, and showing the overlapping and bending nature of the variousbundles of single-wall carbon nanotubes. FIG. 15D shows severaldifferent bundles of single-wall carbon nanotubes, all of which are bentat various angles or arcs. One of the bends in the bundles is relativelysharp, illustrating the strength and flexibility of the bundle ofsingle-wall carbon nanotubes. FIG. 15E shows a cross-sectional view of abundle of 7 single-wall carbon nanotubes, each running roughly parallelto the others. All of the transmission electron micrographs in FIGS. 15Athrough 10E clearly illustrate the lack of amorphous carbon overcoatingthat is typically seen in carbon nanotubes and single-wall carbonnanotubes grown in arc-discharge methods. The images in FIGS. 15Athrough 15E also reveal that the vast majority of the deposit comprisessingle-wall carbon nanotubes. The yield of single-wall carbon nanotubesis estimated to be about 50% of the carbon vaporized. The remaining 50%consists primarily of fullerenes, multi-layer fullerenes (fullereneonions) and/or amorphous carbon.

[0279]FIGS. 15A through 15E show transmission electron microscope imagesof the products of the cobalt/nickel catalyzed carbon nanotube materialthat was deposited on the water cooled collector in the laservaporization apparatus depicted in FIG. 1. Single-wall carbon nanotubeswere typically found grouped in bundles in which many tubes ran togetherroughly parallel in van der Waals contact over most of their length. Thegrouping resembled an “highway” structure in which the bundles ofsingle-wall carbon nanotubes randomly criss-crossed each other. Theimages shown in FIGS. 15A through 15E make it likely that a very highdensity of single-wall carbon nanotubes existed in the gas phase inorder to produce so many tubes aligned as shown when landing on the coldwater cooled collector. There also appeared to be very little othercarbon available to coat the single-wall carbon nanotubes prior to theirlanding on the water cooled collector in the alignment shown. Evidencethat single-wall carbon nanotubes grow in the gas phase, as opposed tofor example on the walls of the quartz tube, was provided in earlierwork on multi-walled carbon nanotubes using the same method. See Guo etal., “Self-Assembly of Tubular Fullerenes,” J. Phys. Chem., Vol. 99, p.10694 (1995) and Saito et al., “Extrusion of Single-Wall CarbonNanotubes via Formation of Small Particles Condensed Near An EvaporationSource,” Chem. Phys. Lett., Vol. 236, p. 419 (1995). The high yield ofsingle-wall carbon nanotubes in these experiments is especiallyremarkable because the soluble fullerene yield was found to be about 10weight percent, and much of the remaining carbon in the soot productconsisted of giant fullerenes and multi-layer fullerenes.

Example 2 Laser-Vaporization to Produce Longer Single-Wall CarbonNanotubes

[0280] In this example, a laser vaporization apparatus similar to thatdescribed by FIG. 1 was used to produce longer single-wall carbonnanotubes. The laser vaporization apparatus was modified to include atungsten wire strung across the diameter of a quartz tube mounted in anoven. The tungsten wire was placed downstream of the target so that thewire was 1 to 3 cm downstream from the downstream side of the target (13to 15 cm downstream from the surface of the target being vaporized).Argon at 500 Torr. was passed through the quartz tube at a flow rateequivalent to a linear velocity in the quartz tube of about 1 cm/sec.The oven was maintained at 1200° C. and Group VIII transition metalswere combined at 1 to 3 atom % with carbon to make the target.

[0281] The pulsed laser was operated as in Example 1 for 10 to 20minutes. Eventually, a tear drop shaped deposit formed on the tungstenwire, with portions growing to lengths of 3 to 5 mm. The depositresembled eyelashes growing on the tungsten wire. Examination of thedeposit revealed bundles of millions of single-wall carbon nanotubes.

Example 3 Two Laser Vaporization

[0282] Graphite rods were prepared as described in Example 1 usinggraphite, graphite cement and 1.2 atom % of a mixture of 50 atom %cobalt powder and 50 atom % nickel powder. The graphite rods werepressed into shape and then formed into targets as described inExample 1. The graphite rods were then installed as targets in anapparatus as diagramed in FIG. 2, except tungsten wire 32 was not used.A quartz tube holding the graphite rod targets was placed in an ovenheated to 1200° C. Argon gas which had been catalytically purified toremove water vapor and oxygen was passed through the quartz tube at apressure of about 500 Torr and a flow rate of about 50 sccm althoughflow rates in the range of about 1 to 500 sccm (standard cubiccentimeters per minute), preferably 10 to 100 sccm are also useful for a1 inch diameter flow tube. The first laser was set to deliver a 0.532micron wavelength pulsed beam at 250 mJ per pulse. The pulse rate was 10Hz and the pulse duration was 5 to 10 ns. A second laser pulse struckthe target 50 ns after the end of the first pulse. The second laser wasset to deliver a 1.064 micron wavelength pulsed beam at 300 mJ perpulse. The pulse rate was 10 Hz and the pulse duration was 5 to 10 ns.The first laser was focused to a 5 mm diameter spot on the target andthe second laser was focused to a 7 mm diameter gaussian spot having thesame center point on the target as the spot from the first laser. About{fraction (1/10)}th of a second after the second laser hit the target,the first and second lasers fired again and this process was repeateduntil the vaporization step was stopped.

[0283] About 30 mg/hr of the raw product from the laser vaporization ofthe target surface was collected downstream. The raw product comprised amat of randomly oriented single-wall carbon nanotubes. The raw productmat is made up almost entirely of carbon fibers 10-20 nm in diameter and10 to 1000 microns long.

[0284] About 2 mg of the raw product mat was sonicated in 5 ml methanolfor about 0.5 hour at room temperature. Transmission Electron Microscope(TEM) analysis of the sonicated product proved that the product wascomprised mostly of ropes of single-wall carbon nanotubes, i.e., bundlesof 10 to 1000 single-wall carbon nanotubes aligned with each other(except for occasional branching) having a reasonably constant ropediameter over the entire length of the rope. The ropes were more than100 microns long and consisting of uniform diameter single-wall carbonnanotubes. About 70 to 90 wt % of the product is in the form of ropes.The individual single-wall carbon nanotubes in the ropes all terminatewithin 100 nm of each other at the end of the rope. More than 99% of thesingle-wall carbon nanotubes appear to be continuous and free fromcarbon lattice defects over all of the length of each rope.

Example 4 Procedure for Purifying Single-wall Nanotube Material to >99%

[0285] Material formed by the laser production method described in U.S.Ser. No. 08/687,665 was purified as follows to obtain a preparationenriched in nanotubes. 200 mg of the raw laser-produced single-wallnanotube material (estimated yield of 70%) was refluxed in 2.6 M aqueousnitric acid solution for 24 hours. At 1 atm pressure the refluxtemperature was about 1200° C. The solution was then filtered through a5 micron pore size TEFLON filter (Millipore Type LS), and the recoveredsingle-wall nanotubes were refluxed for a second 24 hr period in freshnitric acid solution (2.6 M). The solution was filtered again to recoverthe single-wall nanotube material, and the material recovered from thefiltration step was sonicated in saturated NaOH in ethanol at roomtemperature for 12 hours. The ethanolic solution was filtered to recoverthe single-wall nanotube material, and the material recovered wasneutralized by refluxing in 6 M aqueous HCl for 12 hours. The nanotubematerial was recovered from the aqueous acid by filtration, and baked at850° C. in 1 atm H₂ gas (flowing at 1-10 sccm through a 1″ quartz tube)for 2 hours. The yield was 70 mg of recovered purified material.Detailed TEM, SEM and Raman spectral examination showed it to be >99%pure, with the dominant impurity being a few carbon-encapsulated Ni/Coparticles.

Example 5 Procedure for Cutting SWNT into Tubular Carbon Molecules

[0286] Bucky paper (˜100 microns thick) obtained by the filtration andbaking of purified SWNT. material as described in Example 1 was exposedto a 2 GEV beam of Au⁺³³ ions in the Texas A&M Superconducting CyclotronFacility for 100 minutes. The irradiated paper had 10-100 nm bulletholes on average every 100 nm along the nanotube lengths. The irradiatedpaper was refluxed in 2.6 M nitric acid for 24 hours to etch away theamorphous carbon produced by the fast ion irradiation, filtered,sonicated in ethanol/potassium hydroxide for 12 hours, refiltered, andthen baked in vacuum at 1100° C. to seal off the ends of the cutnanotubes.

[0287] The material was then dispersed in toluene while sonicating. Theresulting tubular molecules which averaged about 50-60 nm in length wereexamined via SEM and TEM.

Example 6 Assembly of a SWNT Array

[0288] About 10 ⁶ (10,10) nanotube molecules with lengths 50-60 nm areprepared as described above, are derivatized to have an -SH group at oneend and allowed to form a SAM molecular array of SWNT molecules on asubstrate coated with gold in which the tubular molecules are alignedwith their long axis parallel and the ends of the tubes forming a planeperpendicular to the aligned axes.

Example 7 Growth of a Continuous Macroscopic Carbon Fiber

[0289] The array according to Example 6 can be used to grow a continuousmacroscopic carbon fiber in the apparatus shown in FIGS. 6 and 7. Theends of the nanotubes (which form the plane perpendicular to the axes ofthe tubes) of the array are first opened. For the 2D assembly ofnanotubes on the gold covered surface, the assembly can be made to bethe positive electrode for electrolytic etching in 0.1 M KOH solution,which will open the tips of the nanotubes.

[0290] Ni/Co metal clusters are then vacuum deposited onto the open endsof the assembled nanotubes in the SAM. Preferably, metal clusters 1 nmin diameter are arranged so that one such Ni/Co nanoparticle sits on thetop opening of every nanotube in the nanotube array.

[0291] The Ni/Co capped nanotubes in the array are heated in a vacuum upto 600° C., pyrolyzing off all but the carbon nanotubes and the Ni/Coparticles. Once the pyrolysis is complete, a flow of ethylene gas isstarted, and the tubes elongate in the direction of the aligned axes toform a carbon fiber of macroscopic diameter. If a significant portion ofthe Ni/Co catalyst particles deactivate, it may be necessary toelectrochemically etch the tips open and clean the assembly again, andrepeat steps of applying the Ni/Co catalyst particles and reinitiatinggrowth of the array. A continuous fiber of about 1 micro in diameter iscontinuously recovered at room temperature on the take-up roll.

Example 8 Production of Fullerene Pipes and Capsules

[0292] Single-walled fullerene nanotubes were prepared by an apparatuscomprising a 2.5 cm by 5 cm cylindrical carbon target (with a 2 atom %of a 1:1 mixture of cobalt and nickel) that was rotated about itsprinciple axis in flowing argon (500 torr, 2 cm sec⁻¹) in a 10 cmdiameter fused silica tube heated to 1100° C. Two pulsed laser beams(ND:YAG 1064 nm, 1 J pulse⁻¹, 30 pulse s⁻¹, 40 ns delay) were focused toa 7 mm diameter spot on the side of the rotating target drum and scannedunder computer control along the length of the drum, alternating fromthe left to the right side of the drum so as to change the angle ofincidence on the target surface to avoid deep pitting. This method hasthe advantage of producing 20 grams of material in two days ofcontinuous operation.

[0293] The raw material formed by the apparatus was purified byrefluxing in nitric acid followed by filtration and washing in pH=10water with Triton X-100 surfactant. The net yield of purified fullerenefibers from this method depends on the initial quality of the rawmaterial, which is typically in the range of 10-20% by weight. Themolecular perfection of the side walls, a characteristic of fullerenefibers, allows these fibers to survive the refluxing.

[0294] The fullerene ropes were highly tangled with one other. Thefullerene ropes frequently occurred in fullerene toroids (“cropcircles”), which suggests that the ropes are endless. This is due to vander Walls adherence between the “live” ends of the ropes and the sidesof other ropes during the high-yield growth process in the argonatmosphere of the laser/oven method. The growing rope ends wereeliminated in collisions with another live rope end that was growingalong the same guiding rope from the opposite direction. In onedimension, collisions are unavoidable.

[0295] Ends were created from the tangled, nearly endless ropes by manytechniques, ranging from cutting the ropes with a pair of scissors tobombarding the ropes with relativistic gold ions. Here, the ropes werecut by sonicating them in the presence of an oxidizing acid, such asH₂SO₄/HNO₃. The cavitation produced local damage to the tubes on thesure of the ropes, which activated them for chemical attack by theoxidizing acid. As the acid attacked the tube, the tube was completelycut open and the tube slowly etched back, with its open end unable tore-close at the moderate temperature. Nanotubes underlying the now-cutsurface tube on the rope were exposed, and subsequent cavitation-induceddamage resulted in the cutting of the entire rope. The cut nanotubeswere subjected to further oxidizing acid treatment in order to ensurethat they are molecularly perfect and chemically clean.

[0296] The length distribution of the open-ended tubes is shortenedsystematically with exposure time to the acid. In a 3/1 concentratedsulfuric acid/nitric acid, at 70° C., the average cut nanotube wasshortened at a rate of 130 nm hr⁻¹. In a 4/1 sulfuric acid/30% aqueoushydrogen peroxide (“piranha”) mixture at 70° C. the shortening rate wasapproximately 200 nm hr⁻¹. This etching rate is sensitive to the chiralindex of the nanotubes (n,m), with all “arm chair” tubes (n=m) having adistinct chemistry from the “zig-zag” tubes (m=0), and to a lesserextent with tubes of intermediate helical angle (n≠m).

[0297] The cut fullerene tubes material formed stable colloidalsuspensions in water with the assistance of surfactants such as sodiumdodecyl sulfate or a nonionic surfactant such as Triton X-100. Thesuspensions were separated as a function of nanotube length.

[0298] AFM imaging of the cut nanotube pieces on graphite revealed thatmany nanotubes are individuals, but that a majority of the nanotubeswere in van der Walls contact with each other. The nanotubes withlengths of greater than 100 nm may be closed by true hemifullerene endcaps, which form sealed fullerene capsules when annealed in a vacuum at1000-1200° C.

Example 9 Production and Purification of Fullerene Pipes and Capsules

[0299] Referring to FIGS. 16A-C, a SEM image of raw SWNT felt materialis shown in FIG. 16A, while the same material after purification isshown in FIGS. 16B-C. The abnormally low quality initial startingmaterial emphasizes the effectiveness of the following purificationprocess. The raw sample (8.5 gm) was refluxed in 1.2 l of 2.6 M nitricacid for 45 hours. Upon cooling, the solution was transferred to PTFEcentrifuge tubes and spun at 2400 g for 2 hours. The supernatant acidwas decanted off, replaced by de-ionized water, vigorously shaken tore-suspend the solids, followed by a second centrifuge/decant cycle. Thesolids were re-suspended in 1.8 l water with 20 ml Triton X-100surfactant and adjusted to a pH of 10 with sodium hydroxide. Thesuspension was then transferred to the reservoir of a tangential flowfiltration system (MiniKros Lab System, Spectrum, Laguna Hills, Calif.).The filter cartridge used (M22M 600 0.1 N, Spectrum) had mixed celluloseester hollow fibers of 0.6 mm diameter, 200 nm pores and a total surfacearea of 5600 cm². The buffer solution consisted of 44 l of 0.2 vol %Triton X-100 in water of which the first 34 l were made basic (pH 10)with sodium hydroxide, and the final 10 l at pH 7. The cartridge inletpressure was maintained at 6 psi. A control valve was added to the exitso that the outflow rate was restricted to 70 ml min⁻¹. The result was astable suspension of purified SWNT for which the SEM image in FIG. 16Bis typical. Filtration of this suspension produces a paper of tangledSWNT which resembles carbon paper in appearance and feel. As is evidentin the SEM image of FIG. 16C, the torn edge of this “bucky paper” showsthat the tearing process produces a substantial alignment of SWNT ropefibers. The overall yield of purified SWNT from this abnormally poorstarting material was 9% by weight.

[0300]FIG. 17 shows a taping mode AFM image of cut fullerene nanotubes(pipes) electrodeposited from a stable colloidal suspension onto highlyoriented pyrolytic graphite (HOPG). The tubes had a tendency to align120° to one another. They are in registry with the underlying graphitelattice. AFM measurements of the heights of these cut tubes revealedthat roughly half were single tubes 1-2 nm in diameter, whereas the restare aggregates of several tubes in van der Waals contact. These cuttubes were prepared in a two step process: cutting and polishing. In atypical example, 10 mg of the purified SWNT “bucky paper” (shown in FIG.16B) was suspended in 40 ml of a 3:1 mixture of concentrated H₂SO₄/HNO₃in a 100 ml test tube and sonicated in a water bath (Cole Palmer modelB3-R, 55 kHz) for 24 hours at 35-40° C. The resultant suspension wasthen diluted with 200 ml water and the larger cut SWAT tubes were caughton a 100 nm pore size filter membrane (type VCTP, Millipore Corp.,Bedford, Mass.), and washed with 10 mM NaOH solution. These cut tubeswere then further polished (chemically cleaned) by suspension in a 4:1mixture of concentrated H₂SO₄:30% aqueous H₂O₂ and stirring at 70° C.for 30 minutes. After filtering and washing again on a 100 nm filter,the cut nanotubes were suspended at a density of 0.1 mg/ml in water withthe aid of 0.5 wt % Triton X-100 surfactant. The electrodeposition wasperformed by placing 20 μl of the nanotube suspension on the surface ofa freshly cleaved HOPG substrate (Advanced Ceramics, Cleveland, Ohio),confining the droplet within a Vitron O-ring (4 mm o.d., 1.7 mm thick),capping the trapped suspension with a stainless steel electrode on topof the O-ring, and applying a steady voltage of 1.1 V for 6 minutes.When suspended in water, the nanotubes are negatively charged and aretherefore driven by the electric field onto the HOPG surface. Afterdeposition the HOPG/nanotube surface was washed with methanol on aspin-coater in order to remove the water and the Triton X-100surfactant.

[0301]FIG. 18 shows the Field Flow Fractionation (FFF) of cut fullerenenanotube “pipes” in aqueous suspension. A 20 μl sample of 0.07 mg/mg cutnanotube suspension in 0.5% aqueous Triton X-100 was injected into across-flow FFF instrument (Model F-1000-FO, FFFractionation, LLC, SaltLake City, Utah) operating with 0.007% Triton X-100 in water mobilephase at 2 ml min⁻¹, and a cross-flow rat of 0.5 ml min⁻¹. The solidcurve (left vertical axis) of FIG. 18A shows the light scatteringturbidity (at 632.8 nm wavelength) of the eluting nanotubes as afunction of total eluent volume since ejection. The open circles (rightaxis) plot the estimate radius of gyration of the nanotubes as measuredby a 16 angle light scattering instrument(DAWN DSP, Wyatt Technology,Santa Barbara, Calif.). FIGS. 18B, 18C, and 18D show nanotube lengthdistributions from FFF eluent fractions 1, 3, and 5, respectively, asmeasured from AFM images of the suspended fullerene nanotubeselectrodeposited on HOPG as in FIG. 17.

[0302]FIG. 19 shows an AFM image of a fullerene nanotube “pipe” tetheredto two 10 nm gold spheres, one at either end. The tube waselectrodeposited onto HOPG graphite from a suspension of a mixture ofsuch tubes with colloidal gold particles (Sigma Chemical Co.) in water.The irregularly shaped features in the image are due to residualdeposits of the Triton X-100 surfactant used to stabilize thesuspension. The nanotube-to-gold tethers were constructed of alkyl thiolchains covalently attached to the open ends of the tubes. Presumingthese open ends were terminated with many carboxylic acid groups as aresult of the acid etching in previous processing, they were convertedto the corresponding acid chloride by reacting them with SOCl₂. Thesederivitized tubes were then exposed to NH₂—(CH₂)₁₆—SH in toluene to formthe desired tethers, with the thiol group providing a strong covalentbonding site for a gold particle. Most tubes derivitized this way have asingle gold particle bound to at least one of their ends, as revealed byextensive AFM imaging.

Example 10 Composite Material Containing Carbon Nanotubes

[0303] One gram of purified single walled fullerene nanotubes isdispersed in 1 liter of dichloro-ethane, together with 10 grams of Eponepoxy. The hardener is added to the solvent removed by vacuum rotaryevaporation. The resultant fullerene nanotube-epoxy composite is thencured at 100° C. for 24 hours.

[0304] Alternatively, a carbon fiber, fullerene nanotube composite canbe prepared by drawing one or more continuous carbon fibers or wovencarbon fiber tapes through a vat containing the above dichloroethaneepoxy nanotube suspension, and then winding this impregnated tape arounda desired form. After curing in an autoclave in a fashion known in thecarbon fiber-epoxy composite industry (see, e.g., D. L. Chung, CarbonFiber Composites (1994)), a composite of superior delaminationresistance is produced. The fullerene nanotubes within the compositestrengthen the epoxy between the carbon fiber layers. A superiorcomposite is produced if one uses fullerene fibers for both the woventape layers and the tangled nanotube strengtheners within the epoxyphase.

[0305] Modification and variations of the methods, apparatus,compositions and articles of manufacture described herein will beobvious to those skilled in the art from the foregoing detaileddescription. Such modifications and variations are intended to come withthe scope of the appended claims.

We claim:
 1. A method for purifying a mixture comprising single-wallcarbon nanotubes and amorphous carbon contaminate, said methodcomprising the steps of: (a) heating said mixture under oxidizingconditions sufficient to remove the said amorphous carbon and (b)recovering a product comprising at least about 80% by weight ofsingle-wall carbon nanotubes.
 2. The method of claim 1 wherein saidoxidizing conditions comprise an aqueous solution of an inorganicoxidant.
 3. The method of claim 2 wherein said inorganic oxidant isselected from the group consisting of nitric acid, a mixture of sulfuricacid and hydrogen peroxide, potassium permanganate and mixtures thereof.4. The method of claim 2 wherein said aqueous solution is heated toreflux.
 5. The method of claim 2 additionally comprising the step ofsubjecting the oxidized product of step (b) to a saponificationtreatment.
 6. The method of claim 5 wherein said saponificationtreatment comprises contacting said product with a basic solution. 7.The method of a claim 6 wherein said basic solution comprises sodiumhydroxide.
 8. The method of claim 6 additionally comprising the step ofneutralizing the saponified product with an acid.
 9. The method of claim8 wherein said acid is hydrochloric acid.
 10. The method of claim 8additionally comprising the step of recovering a solid product from thesaponified, neutralized product.
 11. The method of claim 10 wherein saidproduct is recovered by a method selected from the group consisting offiltration, settling by gravity, chemical flocculators, and liquidcycloning.
 12. The method of claim 10 wherein said solid product is apaper-like two dimensional product.
 13. The method of claim 12additionally comprising the step of drying the product.
 14. The methodof claim 13 wherein said product is dried at about 850° C. in a hydrogengas atmosphere.
 15. The method of claim 1 wherein said product comprisesat least about 90% by weight of single-wall carbon nanotubes.
 16. Themethod of claim 1 wherein said product comprises at least about 95% byweight of single-wall carbon nanotubes.
 17. The method of claim 1wherein said product comprises at least about 99% by weight ofsingle-wall carbon nanotubes.
 18. A method for producing tubular carbonmolecules of about 5 to 500 nm in length, said method comprising thesteps of: (a) cutting single-wall nanotube containing-material to form amixture of tubular carbon molecules having lengths in the range of 5-500nm; (b) isolating from said mixture of tubular carbon molecules afraction of said molecules having substantially equal lengths.
 19. Themethod of claim 18 wherein said cutting single-wall nanotubes intotubular carbon molecules comprising the steps of: (a) forming asubstantially two-dimensional target containing single-wall nanotubes oflengths up to about one micron or more, and (b) irradiating said targetwith a high energy beam of high mass ions.
 20. The method of claim 19wherein a high energy beam is produced in a cyclotron and has an energyof from about 0.1 to about 10 GeV.
 21. The method of claim 19 whereinsaid high mass ion has a mass of greater than about 150 AMU.
 22. Themethod of claim 21 wherein said high mass ion is selected from the groupconsisting of gold, bismuth and uranium.
 23. The method of claim of 22wherein the high mass ion is Au⁺³³.
 24. The method of claim 18 whereinsaid cutting single-wall nanotubes into tubular carbon moleculescomprises the steps of: (a) forming a suspension of single-wallnanotubes in a medium; (b) sonicating said suspension with acousticenergy.
 25. The method of claim 24 wherein said acoustic energy isproduced by a device operating at 40 KHz and having an output of 20 W.26. The method of claim 18 wherein said cutting single-wall nanotubesinto tubular carbon molecules comprises refluxing single wall nanotubematerial in concentrated HNO₃.
 27. The method of claim 19 furthercomprising the step of heating the tubular carbon molecules to form ahemispheric fullerene cap on at least one end thereof.
 28. The method ofclaim 18 further comprising the step of reacting said tubular carbonmolecules with a material which provides at the reaction conditions atleast one substituent on at least one of said ends of said tubularcarbon molecule.
 29. The method of claim 26 further comprising the stepof reacting said tubular carbon molecules with a material which providesat the reaction conditions at least one substituent on at least one ofsaid ends of said tubular carbon molecule.
 30. The method of claim 28 or29 wherein said substituent is selected from the group consisting ofeach may be independently selected from the group consisting ofhydrogen; alkyl, acyl, aryl, aralkyl, halogen; substituted orunsubstituted thiol; unsubstituted or substituted amino; hydroxy, andOR′ wherein R′ is selected from the group consisting of hydrogen, alkyl,acyl, aryl aralkyl, unsubstituted or substituted amino; substituted orunsubstituted thiol; and halogen; and a linear or cyclic carbon chainoptionally interrupted with one or more heteroatom, and optionallysubstituted with one or more ═O, or ═S, hydroxy, an aminoalkyl group, anamino acid, or a peptide of 2-8 amino acids.
 31. A method for forming amacroscopic molecular array of tubular carbon molecules, said methodcomprising the steps of: (a) providing at least about 10⁶ tubular carbonmolecules of substantially similar length in the range of 50 to 500 nm;(b) introducing a linking moiety onto at least one end of said tubularcarbon molecules; (c) providing a substrate coated with a material towhich said linking moiety will attach; and (d) contacting said tubularcarbon molecules containing a linking moiety with said substrate. 32.The method of claim 31 wherein said substrate is selected from the groupconsisting of gold, mercury and indium—tin-oxide.
 33. The method ofclaim 32 wherein said linking moiety is selected from the groupconsisting of—S—, —S—(CH₂)_(n)—NH—, and —SiO₃(CH₂)₃NH₃.
 34. A method forforming a macroscopic molecular array of tubular carbon molecules, saidmethod comprising the steps of: (a) providing a nanoscale array ofmicrowells on a substrate; (b) depositing a metal catalyst in each ofsaid microwells; and (c) directing a stream of hydrocarbon or COfeedstock gas at said substrate under conditions that effect growth ofsingle-wall carbon nanotubes from each microwell.
 35. The method ofclaim 34 further comprising the step of applying an electric field inthe vicinity of said substrate to assist in the alignment of saidnanotubes growing from said microwells.
 36. A method for forming amacroscopic molecular array of tubular carbon molecules, said methodcomprising the steps of: (a) providing surface containing purified butentangled and relatively endless single-wall carbon nanotube material;(b) subjecting said surface to oxidizing conditions sufficient to causeshort lengths of broken nanotubes to protrude up from said surface; and(c) applying an electric field to said surface to cause said nanotubesprotruding from said surface to align in an orientation generallyperpendicular to said surface and coalesce into an array by van derWaals interaction forces.
 37. The method of claim 36 wherein saidoxidizing conditions comprise heating said surface to about 500° C. inan atmosphere of oxygen and CO₂.
 38. A method of forming a macroscopicmolecular array of tubular carbon molecules, said method comprising thestep of assembling subarrays of up to 10⁶ single-wall carbon nanotubesinto a composite array.
 39. The method of claim 38 wherein all thesubarrays have the same type of nanotubes.
 40. The method of claim 38wherein the subarrays have different types of nanotubes.
 41. The methodof claim 38 wherein the subarrays are made according to the method ofany of claims 31, 34 or
 36. 42. A method for continuously growingmacroscopic carbon fiber comprising at least about 10⁶ single-wallnanotubes in generally parallel orientation, said method comprising thesteps of: (a) providing a macroscopic molecular array of at least about10⁶ tubular carbon molecules in generally parallel orientation andhaving substantially similar lengths in the range of from about 50 toabout 500 nanometers; (b) removing the hemispheric fullerene cap fromthe upper ends of the tubular carbon molecules in said array; (c)contacting said upper ends of the tubular carbon molecules in said arraywith at least one catalytic metal; (d) supplying a gaseous source ofcarbon to the end of said array while applying localized energy to theend of said array to heat said end to a temperature in the range ofabout 500° C. to about 1300° C.; and (e) continuously recovering thegrowing carbon fiber.
 43. The method of claim 42 wherein said fullerenecaps are removed by heating in an oxidative environment.
 44. The methodof claim 43 wherein said oxidative environment comprises aqueous etchingwith nitric acid or gas phase etching at temperatures of about 500° C.in an atmosphere of oxygen and CO₂.
 45. The method of claim 42 whereinsaid catalytic metal is selected from the group consisting of Group VIIItransition metals, Group VI transition metals, metals of the lanthanideseries, metals of the actinide series, and mixtures thereof.
 46. Themethod of claim 45 wherein said catalytic metal is selected from thegroup consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt.
 47. Themethod of claim 46 wherein said catalytic metal is selected from thegroup consisting of Fe, Ni, and Co, and mixtures thereof.
 48. The methodof claim 45 wherein said catalytic metal is selected from the groupconsisting of Cr, Mo, and W.
 49. The method of claim 42 wherein saidcatalytic metal is deposited in situ on each nanotube as a metal atomcluster.
 50. The method of claim 49 wherein said metal atom cluster hasfrom about 10 to about 200 metal atoms.
 51. The method of claim 42wherein said catalytic metal is deposited as preformed nanoparticles.52. The method of claim 51 wherein said catalytic metal is Mo.
 53. Themethod of claim 42 wherein said catalytic metal is deposited in the formof a metal precursor selected from the group consisting of salts, oxidesand complexes of said metal.
 54. The method of claim 42 when saidcatalytic metal is deposited by evaporating metal atoms and allowingthem to condense and coalesce on said open nanotube ends.
 55. The methodof claim 54 wherein said evaporation is effected by heating a wire orwires containing said catalytic metal.
 56. The method of claim 54wherein said evaporation is effected by molecular beam evaporation. 57.The method of claim 42 wherein gaseous source of carbon is selected fromthe group consisting of hydrocarbons and carbon monoxide.
 58. The methodof claim 57 wherein said hydrocarbon is selected from the groupconsisting of alkyls, acyls, aryls and aralkyl having 1 to 7 carbonatoms.
 59. The method of claim 58 wherein said hydrocarbon is methane,ethane, ethylene, acetylene, acetone, propane, propylene and mixturesthereof.
 60. The method of claim 42 wherein said localized energy isprovided by a laser beam.
 61. The method of claim 42 wherein saidlocalized energy is provided by a source selected from the groupconsisting of a microwave generator, an R-F coil and a solarconcentrator.
 62. The method of claim 42 wherein said end is heated to atemperature in the range of about 900° C. to about 1100° C.
 63. Acomposition of matter comprising at least about 80% by weight ofsingle-wall carbon nanotubes.
 64. The composition of claim 63 comprisingat least about 90% by weight of single-wall carbon nanotubes.
 65. Thecomposition of claim 63 comprising at least about 95% by weight ofsingle-wall carbon nanotubes.
 66. The composition of claim 63 comprisingat least about 99% by weight of single-wall carbon molecules.
 67. Asubstantially two-dimensional article comprising at least about 80% byweight of single-wall carbon nanotubes.
 68. The article of claim 67comprising at least about 90% by weight of single-wall nanotubes. 69.The article of claim 67 comprising at least about 95% by weight ofsingle-wall nanotubes.


73. The molecule of claim 72 wherein said graphene sheet has aconfiguration that corresponds to a (n,n) single-wall carbon nanotube.74. The molecule of claim 72 wherein said molecule has a length fromabout 5 to about 1000 nm.
 75. The molecule of claim 74 wherein saidmolecule has a length of from about 5 to about 500 nm.
 76. The moleculeof claim 72 wherein n is 0 to
 12. 77. The molecule of claim 72 furthercomprising at least one endohedral species.
 78. The molecule of claim 77wherein said endohedral species is selected from the group consisting ofmetal atoms, fullerene molecules, other small molecules and mixturethereof.
 79. The molecule of claim 78 comprising a (10,10) single-wallnanotube containing at last one endohedral species selected from thegroup consisting of C₆₀, C₇₀, or mixtures thereof.
 80. The molecule ofclaim 79 wherein said C₆₀ or C₇₀ additionally contains an endohedralsubstituent selected from the group consisting of metal atoms and metalcompounds.
 81. A macroscopic molecular array comprising at least about10⁶ single-wall carbon nanotubes in generally parallel orientation andhaving substantially imilar lengths in the range of from about 5 toabout 500 nanometers.
 82. The array of claim 81 wherein said nanotubesare of the same type
 83. The array of claim 82 wherein said nanotubesare of the (n,n) type.
 84. The array of claim 83 wherein said nanotubesare of the (10,10) type.
 85. The array of claim 83 wherein saidnanotubes are of the (m,n) type.
 86. The array of claim 81 wherein saidnanotubes are of different types.
 87. The array of claim 81 furthercomprising a substrate attached to one end of said array and orientedsubstantially perpendicularly to the nanotubes in said array.
 88. Thearray of claim 87 wherein said substrate is a bucky paper surface. 89.The array of claim 87 wherein said substrate is a metal layer selectedfrom the group consisting of gold, mercury and indium—tin-oxide.
 90. Thearray of claim 86 wherein a central portion of nanotubes are of the(n,n) type and an outer portion of nanotubes are of the (m,n) type. 91.A macroscopic carbon fiber comprising at least about 10⁶ single-wallcarbon nanotubes in generally parallel orientation.
 92. The fiber ofclaim 91 comprising at least about 10⁹ single-wall carbon nanotubes. 93.A composite fiber comprising a plurality of the fibers of claim
 91. 94.A molecular template array for growing continuous length carbon fibercomprising a segment of the fiber of claim
 91. 95. The fiber of claim 91having a length of at least 1 millimeter.
 96. The fiber of claim 91wherein a substantial portion of said nanotubes are of the (n,n) type.97. The fiber of claim 91 wherein all of said nanotubes are not of thesame type.
 98. A composite article of manufacture comprising a matrixmaterial elected from the group consisting of metals, polymers, ceramicsand cermets, said matrix having embedded in at least a portion thereof aproperty enhancing amount of the carbon fibers of claim
 91. 99. Thecomposite article of claim 98 wherein said property is structural,mechanical electrical, chemical, optical, or biological.
 100. A highvoltage power transmission cable wherein at least one conductorcomprises a continuous carbon fiber according to claim
 96. 101. Thepower transmission cable of claim 100 wherein both a central conductorand a coaxially disposed outer conductor are formed from said carbonfiber and an insulating layer is disposed therebetween.
 102. The powertransmission cable of claim 101 wherein said insulating layer is an airspace.
 103. The power transmission cable of claim 101 wherein saidinsulating layer comprises a material selected from the group consistingof insulating carbon fiber made from carbon nanotubes of the (m,n) typeand insulating BN fiber made from hexaboronitride nanotubes or mixturesthereof.
 104. A solar cell for converting broad serum light energy intoelectrical current comprising a molecular array according to claim 81 asthe photon collector.
 105. The solar cell of claim 104 additionallycomprising a photoactive dye coupled to the upper ends of the nanotubesin said array.
 106. A bistable, nonvolatile memory bit comprising theendohedrally-loaded tubular carbon molecule of claim
 77. 107. The memorybit of claim 106 wherein the tubular carbon molecule is formed from a(10,10) type nanotube and the endohedral species is a C₆₀ or C₇₀fullerene molecule.
 108. A bistable, nonvolatile memory devicecomprising the memory bit of claim 106, means for writing to said bitand means for reading said bit.
 109. The memory device of claim 108wherein said means for writing comprises a nanocircuit element adaptedto direct a voltage pulse of positive or negative polarity at said bitto cause said endohedral species to move from a first end to a secondend of said bit.
 110. The memory device of claim 108 wherein said meansfor reading said bit comprises (a) a first nanocircuit element adaptedto be biased at a first voltage (V_(Read)) and spaced from a read end ofsaid bit to form a first gap therebetween; and (b) a second nanocircuitelement adapted to be biased to ground voltage (V_(G)) and spaced fromsaid read end of said bit to form a second gap, whereby the presence ofsaid endohedral species is unambiguously determined by the presence ofcurrent tunneling across said first and second gaps.
 111. A microporousanode for an electrochemical cell comprising a molecular array accordingto claim
 81. 112. A lithium ion secondary battery comprising the anodeof claim 111, a cathode comprising LiCoO₂ and an aprotic organicelectrolyte wherein a fullerene intercalating compound (FIC) of lithiumforms at the anode under charging conditions.
 113. An apparatus forforming a continuous macroscopic carbon fiber from a macroscopicmolecular template array comprising at least about 10⁶ single-wallcarbon nanotubes having a catalytic metal deposited on the open ends ofsaid nanotubes, said apparatus comprising: (a) means for locally heatingonly said open ends of said nanotubes in said template array in a growthand annealing zone to a temperature in the range of about 500° C. toabout 1300° C; (b) means for supplying a carbon-containing feedstock gasto the growth and annealing zone immediately adjacent said heated openends of said nanotubes in said template array; and (c) means forcontinuously removing growing carbon fiber from said growth andannealing zone while maintaining the growing open end of said fiber insaid growth and annealing zone.
 114. The apparatus of claim 113 whereinsaid means for locally heating comprises a laser.
 115. The apparatus ofclaim 113 enclosed in a growth chamber maintained at a vacuum byevacuation means.
 116. The apparatus of claim 115 further comprising avacuum feed lock zone through which said continuously produced carbonfiber is passed and a take-up roll at atmospheric pressure.
 117. Acomposite material comprising: (a) a matrix; and (b) a carbon nanotubematerial embedded within said matrix.
 118. The composite material ofclaim 117, wherein said matrix comprises a polymer.
 119. The compositematerial of claim 118, wherein said polymer comprises a thermosettingpolymer.
 120. The composite material of claim 119, wherein saidthermosetting polymer is selected from the group consisting ofphthalic/maelic type polyesters, vinyl esters, epoxies, phenolics,cyanates, bismaleimides, and nadic end-capped polyimides.
 121. Thecomposite material of claim 118, wherein said polymer comprises athermoplastic polymer.
 122. The composite material of claim 121, whereinsaid thermoplastic polymer is selected from the group consisting ofpolysulfones, polyamides, polycarbonates, polyphenylene oxides,polysulfides, polyether ether ketone, polyether sulfones,polyamide-imides, polyetherimides, polyimides, polyarylates, and liquidcrystalline polyesters.
 123. The composite material of claim 117,wherein said matrix comprises a metal.
 124. The composite material ofclaim 117, wherein said matrix comprises a ceramic.
 125. The compositematerial of claim 117, wherein said matrix comprises cermet.
 126. Thecomposite material of claim 117, wherein said carbon nanotube materialcomprises tubular carbon nanotube molecules.
 127. The composite materialof claim 117, wherein said carbon nanotube material comprises ropes upto about 10³ SWNTs.
 128. The composite material of claim 117, whereinsaid carbon nanotube material comprises fibers of greater than 10⁶SWNTs.
 129. The composite material of claim 126, 127, or 128, furthercomprising an additional fibrous material.
 130. The composite materialof claim 126, 127, or 128, wherein said carbon nanotube material ismodified to interact with said matrix material.
 131. A method forproducing a composite material containing carbon nanotube materialcomprising: (a) preparing a matrix material precursor, (b) combining acarbon nanotube material with said matrix material precursor; and (c)forming said composite material.
 132. The method of claim 131, whereinsaid carbon nanotube material is combined with said matrix materialprecursor before said step of forming.
 133. The method of claim 131,wherein said carbon nanotube material is combined with said matrixmaterial precursor during said step of forming.
 134. The method of claim131, wherein said carbon nanotube material is combined with said matrixmaterial precursor immediately after said step of forming.
 135. Themethod of claim 131, wherein said matrix material precursor is caused toflow around a pre-formed arrangement of said carbon nanotube material.136. A method of producing a composite material containing carbonnanotube material comprising: (a) preparing an assembly of a fibrousmaterial; (b) adding said carbon nanotube material to said fibrousmaterial; and (c) adding a matrix material precursor to said carbonnanotube material and said fibrous material.
 137. The method of claim136, wherein said fibrous materials are arranged in a two-dimensionalsheet, and some portion of the said carbon nanotube material is orientedin a direction other than parallel to said sheet.
 138. The method ofclaim 131 or 136 wherein said carbon nanotube material comprises tubularcarbon nanotube molecules.
 139. The method of claim 131 or 136, whereinsaid carbon nanotube material comprises ropes of up to about 10³ SWNTs.140. The method of claim 131 or 136, wherein said carbon nanotubematerial comprises fibers of greater than 10⁶ SWNTs.
 141. Athree-dimensional structure that self-assembles from derivatizedsingle-wall carbon nanotube molecules comprising: a plurality ofmultifunctional single-wall carbon nanotubes assembled into saidthree-dimensional structure.
 142. The three-dimensional structure ofclaim 141, wherein said single-wall carbon nanotubes havemultifunctional derivatives on their end caps.
 143. Thethree-dimensional structure of claim 141, wherein said single-wallcarbon nanotubes have multifunctional derivatives at multiple locationson said single-wall carbon nanotubes.
 144. The three-dimensionalstructure of claim 141, wherein said single-wall carbon nanotubes areassembled as a result of van der Waals attractions.
 145. Athree-dimensional structure of claim 141, which has electromagneticproperties.
 146. The three-dimensional structure of claim 145, whereinsaid electromagnetic properties are determined by afunctionally-specific agent.
 147. A three-dimensional structure of claim141, which is symmetrical.
 148. A three-dimensional structure of claim141, which is not symmetrical.
 149. A three-dimensional structure ofclaim 141, which has biological properties.
 150. A three-dimensionalstructure of claim 149, which operates as a catalyst for biochemicalreactions.
 151. A three-dimensional structure of claim 149, whichinteracts with living tissue
 152. A three-dimensional structure of claim149, which serves as an agent for interaction with functions of abiological system.
 153. A light harvesting antenna comprising: at leastone single-wall carbon nanotube conductive element, said at least onenanotube having a length selected relative to a desired current leveland a desired voltage level.
 154. The light harvesting antenna of claim153, wherein said at least one single-wall carbon nanotube forms aSchottky barrier.
 155. An array of light harvesting antennas of claim153.
 156. The array of light harvesting antennas of claim 155, whereinsaid array is formed by self-assembly.
 157. A molecular electroniccomponent comprising at least one single-wall carbon nanotube.
 158. Themolecular electronic component of claim 157, wherein said molecularelectronic component is a bridge circuit for providing full waverectification, said bridge circuit comprising: four single-wall carbonnanotubes, each of said four single-wall carbon nanotubes forming oneedge of a square and linked to two of four buckyballs, each of said fourbuckyballs located at a corner of said square.
 159. The bridge circuitof claim 158, wherein said buckyballs and single-wall carbon nanotubesare derivitized to include functionally specific linking agents.
 160. Amolecular electronic component of claim 157, which is a fullerene diode.161. A nanoscale manipulator comprising at least one single-wall carbonnanotube.
 162. The nanoscale manipulator of claim 161, which isnanoforcepts.